Diode ladar imaging is one of the advanced sensors. It is best suited for the aerospace flight environment. A 4 QK x 8bit pixels/sec diode laser imaging system has been developed by us, and this system was authenticated by specialists last year. This paper describes several important problems for intensity imaging which include improving laser power utilization ratio and receiving sensitivity in laser imaging system. Improvement SNR of imaging system is criterion of analysis and comparsion. Wareform design of the both maximun power limited and average power invariant are analysed separately. In order to understand avalanche gain contribution to receiver SNR, performance comparison of receiving is evaluated for detection type and operation state. The comparison includes intensity modulated (IM) /coherent detection (CD) and IM/Direct detcetion (DD) for different avalanche gain values and different photodetector load resistance values. According to the relations between receivable return power and SNR, a series of curves are calculated by computer. These curves clearly show the best detecting type for various receiver power elevel. These results of analyses provide theoretical basis of transmitter and high sensitivity receiver design. These analyses also show that in intensity imaging system correct waveform selection can make 4dB improvement on SNR and reasonalbe receiver trade-off design can make about 30dB improvement on SNR.