Designed a laser pulse flight time measurement and data processing method based on FPGA in response to the large-scale, high-precision, highly real-time property and lightweight integration requirements of laser ranging technology proposed by intelligent unmanned platform and to solve the problems of system complexity and poor scalability caused by the dependence of traditional laser ranging methods on dedicated time-to-digital converters (TDCs) and constant ratio timing threshold discrimination circuits. The measurement accuracy of 1ns is achieved by FPGA high frequency clock counting + multi-phase time interpolation. A pulse width compensation method is designed to correct the time drift error caused by the change of laser echo power at different distances. The ranging results of the prototype show that the time accuracy reaches 1ns and the measuring error is ±0.15m within the range of 10m-5km, which meets the requirements of large range and high precision at the same time.