Characteristics of seiches in Taihu Lake are analysed preliminarily.The results show that; (1) The os-cilation periods of seiches in East Taihu Lake vary from 180 to 291 minutes,with an average value of 243 minutes and those in West Taihu Lake vary from 120 to 540 minutes with an average value of 400 minutes.(2) The observed maximum amplitude of seiches in Taihu Lake is about 120-130mm.(3) The characteristics of the seiches are estimated by the difference equection, and the estimating error in the periods is about 20 minutes.(4) The water current in the lake by the seiches is quite large.The maximum current speed is about 20cm/s when the seiche amplitude is 100mm.(5) The amplitude variation of seiches is related to the air pressure,wind field and rainfall above the lake.