Based on the long time monitoring data, taking the two typical land-use types(vegetable land and forest) in the plain of Taihu Lake basin as an example, the correlation between soil moisture and precipitation was analyzed with the time series method. The results showed that:(1) Precipitation time series was temporally uncorrelated, soil moisture contents in different depths, however, were self-correlation series.(2) There was a relationship existed between soil moisture and precipitation, the related time was in the range of 1~8 days due to the influence of seasons, soil depths and land-use types.(3) The seasonal change of the related time in forest can be described as:summer and autumn >spring >winter. With the increase of soil depth, the relationship between soil moisture and precipitation showed a trend of decrease in summer and autumn. The correlation in winter and spring, however, were the opposite. In conclusion, the effective time of precipitation on soil moisture was longer in forest than in vegetable land, and the regularity of the relationship between soil moisture and precipitation in forest was much better than that in the vegetable land.