The total structure of a new transverse axial flow threshing and separating unit with double cylinder was described in detail, along with the design scheme of the threshing cylinder and concave. The frontal threshing device was made with the structure of short-rasp-bar, plate teeth, the small distance grid concave, and the posterior threshing device was composed with the structure of the spike tooth cylinder with helical blades and the large distance grid concave. The bench test showed that this device was applied for the large capacity and the difficult threshing rice. It also has the following advantages as higher threshing, lower cleaning loss, the well-proportioned distribution of threshed stuff, and the little trash content, and so on. The field experiment showed that the total loss rate is 1.94%, the threshing loss rate is 0.89%, the broken rate is 0.84%, and the ration of trash content is 0.20% when the feed rate is 4.32kg/s. Various technical indexes have reached to the national standard.