The bipolar junction transistor (BJT) is widely used in pulse generators for the advantages of high switching speed and high repetitive frequency.The ways for BJT performing in avalanche mode were introduced,and the working mechanism of a pulse circuit using BJT was analyzed.In the Marx circuit based on BJTs,the functions of current-limiting resistors,the circuit loss due to resistors and their influence on the magnitude of output pulse were analyzed theoretically and experimentally.The improvements using diodes to replace current-limiting resistors and using traditional Marx structure were proposed.The output pulses of four negative Marx pulse generators with 10-stage in different schemes were compared.It is shown that,the improved circuits have higher pulse magnitude,and the last circuit is the best method whose fall time is shortest and magnitude is highest.Furthermore,the output power increases but the input power decreases.The efficiency of the whole generator is improved.