Abstract: In order to optimizing the process of solid-liquid separation of manure, fresh dairy manure was separated using the developed solid-liquid separator. The water-food ratio, article squeeze gap and screw speed were selected as influence factors, total solid content (TS) after separation was as main inspected target, meantime, productivity of treated dairy manure and solid removal ratio of solid-liquid mixture were selected as independent variables. Based on the quadratic orthogonal rotating combinatorial method with three factors and five levels employed to design the experimental procedure, the effects of independent variables of screw extruded process on solid-liquid separation were analyzed. An optimum independent parameters combination for highest solid TS value of 40% was obtained with water-food ratio of 0.65, article squeeze gap of 1.5 mm and screw speed of 68 r/min. The research results can provide a reference for solid-liquid separation process of dairy manure.