The papain was used to prepare peptides by hydrolyzing protein extracted from cold-pressed sesame cake. The comprehensive impact of the factors on the degree of hydrolysis was studied by orthogonal experiment L16 (45), and the optimal process parameters were substrate concentration 4%, enzyme dose 1 500 U/g, pH 9.0, temperature 60 ℃, time 3 h. In this condition, the degree of hydrolysis could reach 14.98%. The hydrolysate formed a chelate with zinc sulfate. The comprehensive impact of the factors on chelating rate was studied by orthogonal experiment L9（34）. The optimal process parameters were that the ratio of zinc to compound amino acid was 1∶2, pH 7, temperature 60 ℃，stirring in high speed. Under this condition, the rate of zinc chelate was 71.1%. The zinc(Zn2+) chelating peptides were purified with ethanol. The purity of the products could be 99.3%, which contain zinc about 15.62%.