Abstract: Aiming at the shortcomings in present quality evaluation method in threshing and redrying industry, a quality evaluation method based on degree of conformance was proposed by means of normal distribution theory in probability.The effects showed that threshing quality could be effectively evaluated with the method, the disadvantages of traditional evaluation method on the basis of qualified product percentage were overcome, and continuous quality analysis was achieved when the processing indexes of threshing and redrying were not in consistence.