Abstract: The five physical processes used in the limited area model MM5 are disturbed to form a physical ensemble system of 19 members.The abnormal synoptic situation and heavyrain occurred in summer of 1998 in Eastern China was simulated with this physical ensemble system.The outputs from the ensemble simulation are analyzed using the three basic interpretational methods commonly used in the ensemble forecast;the consequence is that it is practicable to introduce ensemble technique in regional climate study.The ensemble technique appends new methods and additional information to regional climate simulation as well.However,there are still some flaws in the ensemble system,the ensemble members are not diverse enough and the range of ensemble simulation is rather narrow,which notonly lowers the accuracy of probability forecast of deviation butalso leads to the actual forecast capability being inferior to the potential one.