With the development of rice harvesting with large scale in China, high-efficiency of combine is more and more important. In order to satisfy the urgent demand of high-efficiency combine, the overall structure of a new crawler type combine with a feed rate of 4~5 kg/s was proposed and the combinational threshing and separating unit with a transverse tangential cylinder and axial rotor was designed. The design focused on the designing process of structural and operational parameters of tansverse tangential cylinder tangential concave, transition section between tansverse tangential concave and rotor concave, axial rotor and concave. Field test showed that the total loss was 1.47% and the damage rate was 0.2%, when the feed rate was 4.86 kg/s, which met the demands of the design.