In order to validate the function and optimize the working parameters of a new stockbreeding mixed rejectamenta separating machine, water ratio, feed rate and rotating speed of flexible sundries separating shaft were taken as the experiment parameters, the recursive model of flexible sundries separating rate was gotten by means of quadratic orthogonal rotation experimental design. Result showed that the equipment could separate the mixture by sundries sort rightly, and the best working parameters combination were water ratio at 87.8%, feed rate at 41.6 L/min, rotating speed at 64.5 r/min, and the suitable rotating speed of the sediment separating shaft taken by additional experiment was 6 r/min. The results can provide references for improving the performance of the separating equipment.