Standard precipitation index (SPI) was used to analyze the annual and growing season precipitation conditions from 1957 to 2012 based on the precipitation data of meteorological station in Wuqi County. The correlation analysis was used between the SPI and the soil water layer thickness of the microtopographies during 2008—2012. The results showed that the precipitation fluctuation was larger from 1957 to 1986 than that from 1987 to 2012. The extreme and severe drought years appeared in 1957—1986, but those did not appear during 1987—2012; there was positive correlation between the SPI of growing season and the change value of soil water layer thickness of microtopographies. The SPI of growing season had the lower correlation degree (R2<0.8) with the gentle slope and sink hole of steep slope, but the R2 lay between 0.8 and 0.9 with gully, platform and ephemeral gully. The SPI of growing season had the larger correlation degree (R2>0.9) with scarp, sunny uniform slope and half sunny uniform slope; and the difference among the change value of soil water layer thickness in the all monitoring points was significant in the growing season, and the mean soil water layer thickness of gentle slope, sink hole and platform was larger than those of other monitoring points.