Pulmonary vein isolation is the cornerstone of catheter ablation for the treatment of atrial fibrillation. (5) the need for a three-dimensional calibration system, ablation catheter and pulmonary vein circumferential calibration catheter, which is expensive, thus affecting the popularization of atrial fibrillation catheter ablation. In view of this, in recent years, international electrophysiologists have developed a number of techniques such as cryoablation, ultrasound ablation and laser ablation to make up for the shortcomings of RF ablation techniques, of which the cryoballoon is the most mature and most accurate new catheter ablation technique. The cryoballoon system (Medtronic, USA) consists of a non-controlled curved, 10F hollow (with a guide wire) catheter with a double-layer balloon at the head end and a N2O refrigeration station (Figure 1). This ultra-low temperature can be used to ablate the heart muscle. The basic steps of applying frozen balloon catheter to electrically isolate the pulmonary vein are: ①After successful atrial septal puncture, the guide wire is placed in the target pulmonary vein with a 14F controlled long sheath, and the balloon catheter is guided by the wire and placed in the connection of the left atrium and pulmonary vein; ②Filling the balloon; ③Injecting the contrast agent into the pulmonary vein through the hollow tube of the guide wire inside the balloon, and if there is no leakage of the contrast agent, it indicates that the balloon has completely blocked the target pulmonary vein If there is no leakage of the contrast medium, it means that the balloon has completely blocked the blood return of the target pulmonary vein; ④ Using the refrigeration system connected to the end of the balloon catheter, the temperature of the balloon is rapidly reduced to below 40℃, thus achieving the purpose of electro-isolation of the pulmonary vein (Figure 2). The key to electro-isolation of the pulmonary vein with a frozen balloon is that “the filled balloon should be connected to the left atrium and the pulmonary vein. A good and complete contact is maintained around the pulmonary vein junction”. If the contact is good, there is no contrast leakage from the target pulmonary vein after contrast injection, and the local temperature decreases rapidly after 90 seconds of cooling (below -45% in the upper pulmonary vein and below -40% in the lower pulmonary vein), and the cooling continues for 300 seconds, most of the pulmonary veins can be electrically isolated (Figure 3). The main complications of cryoablation for atrial fibrillation include: ① phrenic nerve injury (6.38%): the vast majority can be recovered within 1 year. The incidence of phrenic nerve injury was significantly reduced by using a 28-mm cryoballoon (3.53% with a 28-mm balloon and 12.37% with a 23-mm balloon). If the diameter of the right upper pulmonary vein is >25 mm, the incidence of phrenic nerve injury also increases significantly, and cryoablation should be used with caution at this time. (ii) Esophageal ulcer (5.17%): postoperative treatment with acid suppression and mucosal protection can be recovered, and there is no report of left atrial esophageal fistula. ③The incidence of local hematoma was high (1.79%) due to the use of l4F sheath. ④pericardial effusion or compression (1.46%); ⑤pulmonary vein stenosis 0.9% and 0.17% requiring interventional intervention. With the promotion of cryoablation technique for atrial fibrillation and the accumulation of clinical experience, the cryo technique itself is being improved and updated. ①The freezing coil in the cryoballoon is further moved forward, which makes the front end cooling more adequate and uniform. ②The guiding wire also has the function of pulmonary vein potential measurement, playing a “two-in-one” role, eliminating the need to use additional circumferential pulmonary vein measurement electrodes, reducing costs and surgical expenses, facilitating direct monitoring of pulmonary vein potential during ablation, simplifying surgical operation and reducing exposure time. All of these newer cryoballoon techniques will be promoted for clinical use in the near future. In conclusion, the cryoballoon technique can achieve electrical isolation of pulmonary veins, which can effectively treat atrial fibrillation and is particularly suitable for the treatment of paroxysmal atrial fibrillation. Compared with radiofrequency ablation, the cryoballoon technique is easier to operate and has a shorter learning curve, which makes it easier to promote its use; it is generally painless and easier to be accepted by patients; however, the application of cryoballoon technique has a higher chance of phrenic nerve injury, and although most patients can recover, it should still attract the attention of operators. With the improvement of cryoballoon technology, this technology will be more widely used in clinical practice and benefit more and more patients with atrial fibrillation.