There is severe Doppler shift in satellite optical communication, which greatly affects the coherent demodulation and should be eliminated. This paper is a preliminary study of the optical phase-locked loop, using the broadcast ephemeris to estimate the Doppler shift and pulling it down into a range in which it can be captured by digital processing. A comparison is made between the Doppler shift estimation and the true value, which are calculated from GPS broadcast ephemeris data and precise ephemeris data on March 08, 2014, separately.