Abstract: Utilizing the data of water level, observed by tide gauges in Hong Kong, China from 1962? 2017, the variation of sea level, tidal harmonic constants and other character values of water level in the sea area are determined and analyzed in this paper. The results show that the average changing rate of mean sea level is 1.06mm/a, however, both the trend and scale of each tide gauge's mean sea level changing rate are different. For example, the rate of Chi Ma Wan is (-3.85 ± 0.61) mm/a, while the rate of Waglan Island is (4.12 ± 0.76) mm/a and the the rate of Tsim Bei Tsui is (0.32 ± 0.32) mm/a. From 1962 to 2017, S_a and S_sa of Quarry Bay, calculated annually, have poor stability, and the changing trends of harmonic constants of shallow water constituents are obvious relatively. Diurnal and semidiurnal constituents are nearly stable, but in 2004―2008 the amplitudes of M₂, O₁ and K₁ vary from other years. The level of lowest normal low water and lowest astronomical tide increase in the rate of 0.18 mm/a and 0.27 mm/a respectively.