Abstract: Principle of laser detection system based on six quadrants was introduced in this paper. On that basis, a king of digital laser detection system was designed, and a kind of laser ranging method was adopted which based on parabolic interpolation cross-correlation time delay estimation, and the method was able to further improve ranging accuracy. This system adopts dual-channel analog to digital converter to sample the echo signal, and this method of data acquisition performs good real-time. The simulation result indicates that cross-correlation time delay estimation is able to discover the objects of low SNR (R_SN=-7dB) in the laser ranging, and range error is less than 0.74 m.