Due to irregular coastlines, special geological structures and complex submarine topographies, some global ocean tide models exhibit large differences in some specific areas. So that some other geodetic observations have to be used to estimate the ocean tide loading (OTL) under some circumstances as "time-dependent". GPS technique has the advantages of long-term continuous observations, high accuracy and low cost, and GPS precision point positioning (PPP) technique is sensitive to the change of

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... the east, north and vertical component of a station. In this study, it improves that the method in which the 48 OTL displacement parameters estimated in GPS PPP. Then an improved method to estimate 3 time-dependent OTL displacement parameters precisely in PPP is proposed, and the amplitudes and phase lags of eight principal constituents are extracted by the harmonic analysis. 12 GPS stations' continuous observations in Hong Kong from 2006 to 2013 are used to determine three-dimensional OTL displacement by the PPP method. Through comparison of convergence results from static PPP, it is found that the convergence of K1 constituent determined by the method is accelerated in east component. Comparing the RMS misfits between the GPS derived results and the values from the OSU.CHINASEA.2010 ocean tide model, it is found that the constituents' RMS misfits are all less than 1.5 mm in horizontal and vertical directions, except for S2, K2 and K1. Moreover, by comparing the harmonic parameters estimated by GPS derived and tide gauge data with ocean tide models, it is found that the two different observations' results show a great agreement with OSU.CHINASEA.2010 and HAMTIDE2011.11A ocean tide models, which demonstrates that GPS is capable of determining OTL displacement parameters. Using GPS derived 8 constituents' displacements amplitudes and phase lags which were instead of the responding model values to correct OTL can weaken effect of the semiannual signal in GPS long period time series.