The work aims to introduce casein into soy protein to make up for the deficiency of too little Met in soy protein and to improve the functional properties. Soybean protein and casein were used as raw material to introduce soybean peptide (SP) in the casein non phosphopeptides (CNPP) by chymotrypsin catalyzed plastein reaction so as to form soybean protein-casein complexes (CNPSPC), and determine the yield. Then the reaction conditions of CNPSPC were optimized based on the artificial neural network model. When the ratio of substrate addition was 4∶1 (CNPP and SP), the reaction temperature was 46.2 ℃, the reaction pH was 4.97, and the reaction time was 20 h, the yield of CNPSPC reached a maximum of (87.0±0.10)%. This prediction model can optimizer the process of soy protein-casein protein reaction better. The optimized CNPSPC can be used as a good biofilm material.