Two tidal water level data sets, each with a length of 29 days, were obtained from the Swan Lake using a self-recording tide gauge (Model WLR-7 and WLR-8) during November-December, 1998 and August-September, 1999, respectively. Harmonic analysis of the data was undertaken with the method developed by the Proudman Oceanographic Laboratory. The results show that the monthly-average water level in winter is 0.34 m lower than in summer. The tides in the Swan Lake are of a mixed type, which is dominated by semidiural tides, and there exist phase lags in the main constituents between winter and summer. Further, shallow water overtides are significant, in comparison with the main constituents; non-tidal constituents (caused by storms, etc.) in winter are more remarked than in summer. The differences in the tides between winter and summer described above may be caused by atmospheric factors.