Ensemble Kalman filter(EnKF) is used to assimilate the sounding data of a torrential rain process in July 2005 into the mesoscal model MM5.The experiment results show that under the assumption of perfect model,the analysis of EnKF assimilation is closer to the real observations,and the emsemble prediction with the EnKF assimilation is better than that without the EnKF assimilation and the single numerical prediction without adding perturbations.