A pulsed laser ranging system has a wide range of applications in different fields and its ranging accuracy depends on its time measurement accuracy. Because of some shortcomings, it is difficult for a traditional time measurement method to implement pulsed time measurement with high accuracy and sensitivity. A time-to-digital converter chip TDC-GP2 is described in detail. The chip utilizes the delay of logic gates to implement high accuracy time measurement. When it is used with a coarse counter, its maximum measurement range is 4 ms. On the basis of range 1 of the TDC-GP2 chip, high accuracy time measurement with typical resolution of 50 ps RMS in a measurement range from 0 to 1.8 μs can be implemented. This study is in a leading level among all kinds of time measurement methods.