The Regional Climate Model RegCM3 has been integrated to simulate the east Asian summer monsoon in 1994 with three cumulus parameterization schemes (CPSs), respectively. Comparisons between simulations and observations suggest that the model can reproduce the regional circulation systems basically with all three individual CPSs. However, it is not so well when tropical cyclones (TCs) are active over the Western Pacific Ocean (WPO). The model exhibits a common feature when TCs are over WPO in model domain, which gives an anticyclonic circulation difference over WPO, and two cyclonic circulation differences centered over eastern China/Yellow Sea and Japan/WPO to the east of Japan, depending on the adopted CPS. With a smaller model domain, the model can give a more reasonable result over east Asia forced by reanalysis data. We argue that the unsuccessful simulations in summertime over east Asia are partly caused by the models' failure to capture the features of TCs over WPO.