Advantages: non-invasive, no side effects, no damage to the health of the person being examined, simultaneous analysis of the breathing and ECG disturbances that occur during the patient’s sleep, and understanding of the causal relationship between them. Monitoring indicators are comprehensive. Disadvantages: The cost of the examination is relatively high, usually about hundreds of dollars. Patients generally need to sleep in the sleep center, more electrodes installed, easy to interfere with the patient’s sleep, especially in mild patients, sometimes due to poor sleep resulting in the failure of the examination, but the chances of this situation is less. PSG examination before precautions: 1, a few hours before the examination prohibited coffee, tea and other beverages with stimulating effects, because they make people excited, difficult to sleep, but also excite the respiratory center, so that changes in the condition, it is difficult to reflect the normal condition. 2, forbidden to take sedative sleeping drugs, alcohol, because they can aggravate sleep apnea, and has a certain degree of danger. 3, many physiological signals are recorded through the electrodes attached to the surface of the skin, good contact is the key to ensure high quality signals, so it is best to wash your hair, shower and shave before the examination. 4.It is better to postpone the examination when you are suffering from cold and other diseases. 5, try to maintain a calm mood, avoid excessive excitement and affect sleep.