In a laser reflective tomography imaging radar system, the narrower the laser pulse is, the higher imaging resolution the system has. But it is difficult to design a large bandwidth and undistorted photoelectric detection circuit. An avalanche photodiode (APD) model and its main parameters are analyzed in detail. An appropriate detector is selected. After the preamplifier, main amplifier and automatic gain amplifying circuits are analyzed, a proper circuit structure is designed. When the GHz-level weak photoelectric signals are being received, they are easy to interfer with the external noise introduced. This may cause the received waveform to be distorted. By using an electromagnetic radiation shielding method to remove the interference, a 1 ns narrow pulse laser signal without distortion is received. The imaging resolution requirement of 0.15 m for the laser reflective tomography imaging radar system is met.