In order to solve the problems of grain loss，breakage and impurity in sorghum harvest，the influence of maturity and mechanical harvest rate on the effect of combined harvest was studied. Taking Jinza No.22 sorghum as the research object，the plot experiment scheme was adopted，and three mechanical harvesting rates were set at the milk ripening stage，wax ripening stage and complete ripening stage，respectively，and the mechanical harvesting rates were set at 0.5 m/s，1.0 m/s and 1.5 m/s，and the indexes such as crushing rate，impurity content，total loss rate and moisture content were measured，so as to obtain the influence rules of mature stage and mechanical harvesting rate on the harvesting effect. The results showed that the maturity stage and mechanical harvest rate had significant effects on the harvest indexes of sorghum，such as impurity content，crushing rate and total loss rate，and the most influential factors on the three harvest indexes were maturity stage. The best results can be achieved when the wax is ripe and the mechanical harvest rate is 1.0 m/s，when the grain moisture content is from 14.756% to 15.746%，the impurity content is 0.14%，the crushing rate is 0.29% and the total loss rate is 5.48%. This study obtained the influence law of mature period and mechanical harvest rate on sorghum harvest effect，which can provide theoretical basis for reasonable selection of mature period and popularization of harvesting technology of sorghum mechanization.