Base on the data of daily temperature from 1981 to 2012 and the rolling forecasting of daily temperature in March 2014 at the Haidian meteorological station, the predicting of first flowering date of Prunus discoidea in Beijing Yuyuantan Park is conducted by using the SW Phenological Model. The results show that the errors between the predicted and observed first flowering dates of Prunus discoidea are 3 to 4 days, to predict 10 days ahead of time, and 1 to 2 days, to predict 7 days ahead of time. The deviations of daily temperature prediction are the main cause. The results indicate that the SW model is applicable and well worth popularizing.