Abstract: In order to clarify the influence of diurnal variation of sea surface temperature (SST) on regional climate over coastal waters of China, two sensitivity experiments have been conducted using a regional climate model forced by both hourly-mean SST and daily-mean SST for 20 years (1991-2010). Although the main characteristics of climate over the coastal region of China can be well simulated by these two sensitivity experiments, there still exist some significant differences between them. For the sensitivity experiment forced by hourly-mean SST, the temperature at 2 m (T2) and the sensible heat flux tend to have positive anomalies in the summer and negative anomalies in the winter, while the tendency of the latent heat flux is opposite. In the summer, southeasterly wind anomalies blowing from the ocean to the land prevail in the lower levels; in the winter, northwesterly wind anomalies blowing from the land to the ocean are the primary features. For water vapor transport, positive/negative rain anomalies always correspond to cyclonic/anticyclonic circulation anomalies. The influence of diurnal variation of SST over the coastal waters of China on these climatic variables are much more significant in the summer than in the winter.