It is subjective to calculate the runoff from rainfall by soil conservation service(SCS) model due to the large differences of CN parameter among regions. In attempt to get the particularly suitable CN parameter for the red soil region, the CN parameter was calculated based on runoff and rainfall data from the observation plots of Yanjiagou watershed in De'an County of Jiangxi Province during 2001-2003. The regression analysis between rainfall and CN parameter produced the CN simulation functions for different runoff plots. The result indicated that the reliability of CN simulation functions of different runoff plots were very well. Meanwhile, it also showed the feasibility of the application of SCS model in estimating runoff volume in slope field of red soil.