ECG leads mainly include chest leads and limb leads, which are located in the corresponding limbs and the back of the chest of the human body. General standard ECG 12 leads, mainly chest leads V1-V6; limb leads I, II, III standard limb leads and aVR, aVL, aVF pressurized limb leads. The position of the electrodes of the thoracic leads V1 lead electrode was located in the 4th intercostal space at the right edge of the sternum, V2 lead electrode was located in the 4th intercostal space at the left edge of the sternum, V4 lead was at the junction of the left midclavicular line and the 5th intercostal space, V3 lead was at the midpoint of the connecting line of the V2 and V4 leads, V5 lead was at the same level as the V4 lead in the left anterior axillary line, and V6 lead was at the same level as the V4 lead in the left midaxillary line. The limb leads were mainly made of 4 different colored clips at the limbs, the red clip should be clipped at the patient’s right upper limb wrist, the black clip at the patient’s right lower limb ankle, the yellow was clipped at the left upper limb wrist, and the green was clipped at the left lower limb ankle. When posterior wall infarction is suspected, 18 leads are needed, and V7, V8, V9, V3R, V4R, and V5R leads are needed on top of the 12 leads. The V7 lead electrode is located in the posterior axillary line, the V8 lead electrode is located in the posterior scapular line, and the V9 lead is on the left side next to the spine.The V3R, V4R, and V5R leads are all located in the right chest, in the positions corresponding to the V3, V4, and V5 leads. The operation of ECG needs to be completed by a professional physician, do not operate on your own to avoid errors that cause inaccurate results and affect the judgment of the condition.