Abstract: The configuration, failure mechanism and heat generation mechanism of highpower diode laser (HDL) are described. The lifetime assessment is discussed, including the methods used and the difficulties encountered in the assessment. The status quo of such assessment at home and abroad is given. Some suggestions on lifetime assessment and test are given. The development of reliability and lifetime test for high power diode laser is promoted by its application in civilian industry, military and space filed. With the increasing of reliability and lifetime, high power diode laser will find more applications.