The transmitter is an important part in CINRAD/SA radar. Because of its comp lex structure and running in the state of uninterrupted high voltage, a highest failurerate occurs among several extensions of radar system. Generally, th e rad ar system will be forced to halt once this fatal failure occurred. Based on an a b normal CINRAD/SA radar transmitter power decline, we find out that the failure lie s in the highfrequency pulse generator, which makes the pulse width depressed. And also, some maintenance methods are summed up here, from which the rad ar maintenance professional could take as reference.