This paper presents the stability analysis and design of a mono-pulse photoelectric detecting system, which consists of a laser diode and a photoelectric detector array. The laser source is a laser bean and the response of the detector is a mono-pulse small signal. The pulses type height is 100mV and type width is 1mS. System can detect the laser beans position on the detector target thought mono-pulse detecting. After signal analysis and signal processing, the Interference is reduced, the multi-response is resolved and the mono-pulse is detected well.