Abstract: The model of rigid cascade was built up in this paper. The model has two pipe lines, and there is waste orifice plate in each stage of rigid cascade. The parameters influencing effect of rigid cascade are mainly orifice plate size and feed flow. The two factors were analyzed and compared. The calculation results indicate that the product concentration minishes with the increase of feed flow. The influence on waste was obvious. The influence of orifice plate size on the product in cascade is larger than that on waste. When the orifice plate size deviates to the original size, smaller size is chosen.