Aiming at the threshing loss during super-rice and round-grained rice harvesting, the head-feed coaxial differential rotor was designed. The threshing test between the different speed and single speed rotor was preceded. The 3-D image and mathematical modal were built by Matlab on the basis of measured data of mixture and its compositions. The results showed that the 0.06% grains were not threshed clearly by differential rotor, which reduced by 61.25% compared to the single speed one. The 3-D image showed that uniform distribution of mixture and its compositions along on sieve was better than the single speed one. The coaxial differential threshing rotor set the benefit of high-speed and low-speed in one, which can solve the problem of the threshing loss during super-rice and round-grained harvesting and reduce the loss rate, the damage rate and impurity loss.