Clock error measuring method of satellite-to-earth time system

A clock error measuring method of a satellite-to-earth time system is disclosed, comprising the following steps of: firstly, transmitting a group of laser pulses to a satellite by a ground station, wherein the transmission time tsend is fixed at a TG moment before the exact second of a ground timing system; reflecting the received laser pulses back to the ground station by a laser reflector on the satellite, and simultaneously, measuring the time difference between a moment when the laser pulses are received and the clock of the satellite in real time by a satellite time difference measuring system, thereby obtaining a group of time difference data; filtering the time difference data by using a double histogram method so as to determine the selected time difference data TS; recording a moment trev when the laser reflected by the laser reflector on the satellite is received on the ground, and taking the difference between the trev and the tsend as a laser round time tau measured by a ground laser distance measuring station; and finally, calculating the clock error delta T of the satellite-to-earth time system through a formula and downloading the clock error delta T to the ground station.