Abstract: Tilapia scale is one of the by-products of tilapia machining process.There are about 4×10⁴ tons of tilapia scales every year around the whole world.Though the yield of tilapia scale is very considerable,it has not been fully utilized.Tilapia scale is a dominant raw material in extracting protein and it is conducive to the realization of the aim of turning waste into treasure.Enzymes are biological macromolecules having biocatalyst functions,which generally consist of amino acid,so most of them are protein essentially.Enzymes have some characters,such as high efficiency,specificity and instability.Therefore,different enzymes must be selected for specific raw material,the optimal hydrolysis conditions need to be researched.Enzyme dosage,hydrolysis time,substrate concentrations and hydrolysis temperature are the main factors which play important roles on hydrolysis effect.Collagen peptides emerging as a new functional protein ingredient were developing rapidly in domestic and abroad in recent years.In order to investigate the theory for deeper research of tilapia scale,the optimum extracting conditions of collagen peptides from tilapia scale were carefully and comprehensively studied in this paper.Scale was processed by washing,acid leaching,and alkaline leaching.Then collagen was extracted by using boiled water to incubate for 2 hours.Tilapia fish scale collagen protein was hydrolyzed by enzyme and hydrolysis degree of hydrolyzed liquid was detected.The optimal enzyme was selected in the norm of the hydrolysis degree of hydrolyzed liquid,and then the influences of enzyme dosage,hydrolysis time,substrate concentrations and hydrolysis temperature on hydrolysis degree were studied.Based on the single factor experiment results,orthogonal experiments were carried out to research the optimal hydrolysis conditions.The results showed that:in the conditions of enzyme dosage 6 000 U/g,hydrolysis time 8 h,substrate concentrations 5%,hydrolysis temperature 50℃,the hydrolysis degree of tilapia scale collagen protein peptides reached a maximum value,which was 24.23%,and the molecular weight of the 82.40% sample was less than 1 000 Da.