Using different assimilation methods, data from automatic stations and precipitable water vapor (PWV) data from GPS stations in the Tibetan Plateau and its vicinity are assimilated, in order to investigate the role played by these observations in summer rainfall prediction in China. Through comparing assimilation results and precipitation forecast results of two months in summer of 2008, the main conclusions can be drawn from this paper as follows: Firstly, as the average height of these observational stations is above 2550 m, the positive effects to adjust the background fields are concentrated on the pressure above 500 hPa after assimilating the observations in the Tibetan Plateau and its vicinity; The adjustment using intermittent assimilation is more obvious than using single assimilation, especially above 500 hPa. Secondly, regardless of intermittent assimilation or single assimilation, the improvements of precipitation forecast in North China are less obvious, except for individual precipitation levels. Thirdly, using single assimilation can improve obviously the rainfall forecast in eastern Southwest China; In most cases, precipitation forecast results obtained by assimilating the 7 stations’ observations along 99° E are more accurate than by assimilating the 24 stations’ observations. Fourthly, using intermittent assimilation is more conductive to the precipitation forecast in the Yangtze River areas, especially for the 25-48 h precipitation forecast; At the same time, the precipitation forecast by assimilating 24 stations’ observations is superior to the one by assimilating 7 stations’ mostly.