The Severe Weather Automatically Nowcast System (SWAN) has been widely used in weather nowcasting operation. The technology and features of radar quantitative precipitation estimation (QPE) are introduced. The practicability of QPE is evaluated, and the causation of QPE error is preliminarily analyzed, selecting the data during rainstorm weather from 6 Sband Doppler weather radar sets in 2012 in Hubei Province. The results show that the mean absolute error rate (MAER) is below 30% overall; the increasing range of radar has little influence on QPE precision; the MAER is keeping small in above 30 mm cases, while QPE is underestimated comparing with rain gauge records; moreover, the proportion of the underestimated is increasing in heavier rainfall. Concerning a single radar set, the worst is in Yichang due to the radar beam blocking of mountains, and worse in Wuhan due to the radar beam blocking of buildings, and the best is in Enshi.