Abstract: A newly compact high-precision timing discrimination circuit based on constant fraction discrimination was designed, which was adapted extraordinarily to laser proximity fuze. A biased switch compensation technology was adopted to counteract the crossing zero walk error caused by charge accumulative action, which meant that the biased voltage was decided by the laser echo amplitude. The timing discrimination error of the improved constant fraction discrimination was analyzed with lots of detailed experiments, The experiment results indicated that the timing discrimination error caused by the amplitude variation and the noise variation of the received signal was less than 125 ps, when the SNR was more than 20 and the input signal is 0.2 V to 2.134 V (20.12 dB dynamic range). The error was less than 100 ps when the SNR more than 60. Furthermore, Detection on the whole system integrating the timing discrimination circuit verifies that, the laser repetition frequency can reach 20 kHz, the single shot standard deviation is about 1.45 cm over 20 m ranges, which improve greatly the fixed distance precision of laser proximity fuze.