In order to solve major problems of the high power consumption of threshing and separating of rice combine harvesters, more short trash in product, uneven distribution, and so on, a new threshing drum with short-rasp-bar tooth was developed, and then the experiments were conducted. The experimental results show that this new device has lower power consumption while threshing rice, less impurity contents and comparative uniform distribution, thus reducing the cleaning load effectively. Furthermore, by means of regression analysis, applying DPS software, the mathematical models of threshing and separating systemshort-rasp-bar-plate tooth drum were established with grid concave, including threshing and separating grain losses rate, power consumption and distribution of outlier along cylinder’s axial direction. Lastly, a multi-objective optimization was applied on the system based on Matlab optimum toolbox, so as to get the comprehensively optimistic operating parameters.