Pulsed time-of-flight laser altimeter operates by transmitting a short laser pulse to an optical visible target and by detecting the reflected pulse with an optical detector. The measured distance is calculated from this flight time. So the accuracy of laser time interval is a basic beacon to measure its system capability. We use a special time-digital-converter chip to develop a high resolution time interval module. Based on delay chain,it has high frequency and precision,suffer no outside environmental interference,completely suite for laser altimeter. Finally the soft and hardware realization method and measurement result are given.