In this study, RSM (Regional Spectral Model) was designed for the 12/1985-12/1995 simulation of Vietnam summer monsoon characteristics based on the initial and boundary conditions driven by R2 (NCEP/DOE Reanalysis-2; by global 2.5deg). The assessment results showed that, RSM can display the basical wind circulations in different atmospheric layers (850 hPa, 500 hPa, 200 hPa) during the summer monsoon in Vietnam. However, the simulation error was quite clear in the circulations of various layers of the atmosphere, and the clearest error was found in the 500 hPa layer. In the 850 hPa and 200 hPa layers, the clearer errors were found during the first month and last month of the summer monsoon season. Normally, the RSM model showed the weaker intensity of summer monsoon than CFSR. In addition, the RSM model showed the pentad started later and ended sooner in the summer monsoon; therefore, the duration of summer monsoon was shorter than the real observation. In term of the summer rainfall characteristics, the RSM model showed the 30-80 mm/month lower total rainfall than the stations’ observation over Vietnam. Nevertheless, the RSM model showed quite well the intraseasonal and interannual variabilities of the monsoon intensity, pentad of onset and withdraw, and summer monsoon rainfall.