Orthogonal experiment of threshing and cleaning parts of 4LZ-1.0Q cereal combine harvester was designed. Wheat field experiments with fuzzy analysis of synthesize evaluation were analyzed. The optimized group of parameters in roller, concave board screen, cover plate, vibration sieve and centrifugal blower was got. Test results indicated the sequences of factors influencing the threshing performance were roller linear velocity, separating interval, guide number of cover plate, mesh size and screening area of concave board screen and threshing interval. The values were 25 m/s, 55 mm, 4, 204°, 36 mm×15 mm and 15 mm, respectively. The sequences of factors influencing the cleaning performance were vibration sieve crank rotating speed, vibration sieve type, centrifugal blower rotating and amplitude of vibration sieve. The values were 404 r/min, 16 mm, 1787 r/min and 30 mm. Thus, the impurity rate was less than 3%, the broken rate was less than 1% and the loss rate was less than 1.5%.