Abstract: In order to improve the shelling rate and reduce the breakage rate, the central composite experiments were conducted to optimize the working parameters. Firstly, the physical properties of coix lacryma-jobi were studied, and the study object was "White shell coix lacryma-jobi" planted widely in Guizhou Province, the shape of which was irregular, and the thousand kernel weight was 86.5g. Proportion of thickness δ≤5 mm was 25%, 5＜δ≤5.5 was 58%, and others were δ＞5.5. The weight ratio of shell and kernel was 1:2.5. The moisture content of shell and kernel was 11.6% and 12.7% respectively. The crushing force of coix lacryma-jobi was 45 N≤F≤95 N, 60% of which was about 65 N. The flow angle of coix lacryma-jobi tested by inclined surface device was 14.5°. Based on composite experiment methods of quadratic orthogonal rotation, the effects of key components' main working parameters of coix lacryma-jobi sheller on shelling rate and breakage rate were analyzed, the parameters include rotation speed of rotary plate, distance between rotary and stationary plate, working face width of stationary plate, and the data were analyzed based on the Design-Expert software. The mathematical regression models of shelling rate and breakage rate were built, and corresponding variance analysis were conducted. A regression equation of the relationship between variation coefficient of 3 main working parameters was obtained. Through the analysis of variance, the results showed that the most influential factor for shelling rate was the rotation speed of rotary plate, and the minimum impact factor was the distance between rotary and stationary plate; regarding to the breakage rate, the most influential factor was working face width of stationary plate, and the minimum impact factor was the rotation speed of rotary plate. The response surface method was utilized to analyze the effects of factors' interaction on shelling rate and breakage rate, and the multi-objective optimizations were conducted for the regression models to obtain the working parameters for the best shelling rate and the lowest breakage rate. The optimal combination working parameters of key components of coix lacryma-jobi sheller were the speed of rotary plate was 1 076.02 r/min, the distance between rotary and stationary plate is 4.91 mm, and the working face width of stationary plate of 7.63 mm. Under the condition of the optimal combination working parameters, the shelling rate and breakage rate was 50.49% and 3.02%, respectively. The production verification test was conducted in factory. With the optimal parameters of coix lacryma-jobi sheller, the shelling rate was improved greatly, and the shelling rate and breakage rate was 51.1% and 3.6%, respectively, which close to the results obtained from the previous model. The study provides the scientific basis for key components' working parameters optimization of coix lacryma-jobi sheller.