This study examines the performance of the WRF-Single-Moment-Microphysics scheme (Hong et al. 2003). Recently, Hong et al. (2003) proposed a significantly revised ice microphysical processes after Rutledge and Hobbs (1983) and Lin et al. (1983), based on a new assumption for ice crystal number concentration being a function of ice amount, and related changes in microphysics. They showed a better precipitation and large-scale temperature forecasts in the Weather and Research Forecasting model (WRF) within simple and mixed phase schemes for a heavy rainfall case over Korea on 24-25 June 1997. In this study, we conduct the sensitivity tests due to new ice-microphysics of the Hong et al. for a band type heavy rainfall case over Korea on 14-15 July 2001 and the other mesoscale convective system developed in the Central Great Plains of United States on 15 June 2002. In addition to simple (WSM3) and mixed phase (WSM5) schemes developed in the Hong et al., the graupel substance is added to be another prognostic variable (WSM6). Overall, the new ice-microphysics produces more realistic vertical distribution of hydrometeors, irrespective of the number of prognostic water substance. For the heavy rain case over Korea, the impact of new scheme was not significant but simulates the rain band southward which is closer to the observation. Impact of the complexity of microphysics in the WSM modules on the simulated convective systems is investigated. The results from the WSM physics is also compared with that of Lin et al.