There are several coastal upwelling areas in the Taiwan Strait. The most active and the longest term duration upwelling areas are located at the east side of Haitan Island, south-east side of Dongshan Island and south side of Taiwan Shoal. In this paper, the causes of generation, evolution and decay process of upwellings off the western coast of Taiwan Strait were analysed by using historical weather data, current and seawater temperature data obtained from 1983 to 1989. The influences of dynamical factors (such as currents, monsoon and tide mixture)were evaluated and compared. Results showed that current and monsoon are the main causes of the generation, evolution and decay process of upwellings off the western coast of Taiwan Strait. Because of the instability of monsoon speed and the discontinuity of longshore wind, the main factor influencing the generation and maintainance of coastal upwelling in the research area is current.