Qinghai from July to September in 2003, 2004. The cl oud water feature was analyzed by using the data from the microwave rad iometer, and an experiment of weather modification is preliminary conducted. Th e result indicated that there is a certain range of both Q and L under t he vario us atmospheric conditions, for which the retrieval model is effective. For the c umulonimbus case, there is an obvious fluctuation in both Q and L in adv ance of five hours of precipitation. Then, the convective cloud developed and Q and L ha d a sharp increase. Data comparison between Henan and Xi’an stations shows that Q and L were influenced by the terrain and vapor transportation. The fo rmer sta tion has a better potentiality of precipitation enhancement than t he later. The calculated threshold of precipitation has reference value for the operation of weather modification in the upper reaches of the Yellow River.