The invention discloses a system to reduce the influence of wearable medical device alarm on the sleep quality. The system includes a detection module, a sleep detection module, a master control module and an alarm module, wherein the detection module is used for detecting vital sign parameters of patients in real time and sending the vital sign parameters to the master control module, the sleep detection module is used for detecting sleep states of the patients and sending the sleep states to the master control module, the master control module is used for dividing out different alarm cyclesaccording to the vital sign parameters and the sleep states of the patients and then driving the alarm module to alarm, wherein the alarm cycles include but are not limited to normal sleeping periods,early warning periods, half waking periods, full waking periods and treatment periods, and the alarm module is used for waking up the patients by adopting alarm methods with different intensities according to the different alarm cycles to reduce the influence on the sleep quality of the patients. The invention further discloses a method to reduce the influence of the wearable medical device alarmon the sleep quality. According to the device and the method, necessary alarm to the patients under abnormal conditions can be ensured, and meanwhile the influence of the alarm on the sleep quality of the patients can be further lowered.