The reliability of packaging technique about diode laser (DL) unit and the defect characteristics of high power DL stack and pumping module are analyzed. Testing methods for the reliability of high power DL unit and stack is made. Random samples selected from the lasers passing the reliability tests were used for lifetime test. Under the conditions of cooling water temperature of 20 ℃, current of 150 A, and duty cycle of 15% (500 Hz, 300 μs), the experimental results led to an estimated lifetime of 5×109 shots. No defect was found during the lifetime test. It was demonstrated that the reliability of diode lasers could be assured after filtrating.