Method for determining periodical GPS signal emission time

The invention discloses a method of using satellite to transmit periodical event information to determine periodical GPS signal transmitting time, selecting a known GPS periodical event signal; letting the periodical event signal make coherent integration with the GPS signal and making time-domain and frequency-domain peak value detection on the coherent integration value, after waiting a cycle of periodical event, when still able to detect the periodical event signal, judging the periodical event signal has been received, and then obtaining accurate GPS time based on the time when satellite transmits the periodical event according to the function of periodical event and GPS system time. When the GPS signal power and noise power spectrum density are lower than 30dB-Hz, even 20dB-Hz, it can still obtain accurate GPS time when signal is transmitted, so that the GPS receiver can still accurately position in the environment of weak signal.