Abstract: Taiwan Strait has the second largest tide areas and the second smallest tide areas except for amphidromic points in China. As the main composition of the tide，M₂ causes a controversy on the mechanism of tidal structure formation. In this paper， a numerical model of tide and tidal currents in Taiwan Strait is established based on MIKE 21 with a good agreement with long-term observation data of 20 tide observation stations and 4 ADCP observation stations. The distributions of co-tidal， tide ellipse and tidal energy flux for M₂ tide are given. To explore the formation mechanism of M₂ tide， two sensitivity tests for the topography and southern open boundary conditions were carried out. The results show that the southward incident wave from the East China Sea is reflected to north with a similar phase-lags from the Luzon Strait by the abruptly deepened topography in the south of Taiwan Strait. Two waves transport to the north， and the peak of amplitude occurs where the phase-lags are same， which is the reason of the strong tidal zone in the west of Taiwan Strait. The waves from the Luzon Strait， with contrary phase-lags to the reflected waves also strengthen the amplifications in the west of Taiwan Strait and it is the main reason for tidal band in the southern of Taiwan Strait．