Using the sounding data of Beijing meteorological station (station ID: 54511) in the summer of 2008(1 June to 31 August) as the observed data, the sounding forecasting performances of Beijing rapid update cycle of assimilation forecast system (BJRUC) were analyzed in detail from the aspects of different levels, elements and forecast range. The results showed that the meteorological elements of the BJRUC system have a very good consistency with the real sounding results. The forecast results have better performance in the midlayer than the higher and lower layers. For different meteorological elements, the forecasting capability to the temperature and wind is superior over other elements, and the performance of the humidity is the worst. The forecasting results of the temperature, humidity and southerly wind are too big, but results of the westerly wind are too small. The forecasting performance becomes worse with the increasing of the forecast range, and the results within 12 hours initialed from 12 UTC is better especially. The forecast results of temperature and dew point temperature of midlower layer can be revised with system errors. In general, the forecasting sounding information of BJRUC has a superior performance within 12 hours, which is very useful to the veryshort range weather forecast.