A novel method for preparing an active protein peptide from connective tissue which includes steps of: connective tissue acquisition, segmenting, washing, pulverization, pH adjustment, enzymolysis, filteration, ultrafiltration, nanofiltration concentration, sterilization, freeze-drying, etc. The connective tissue protein peptide obtained by the method of the invention has features of high peptide content, high activity, etc., and the prepared active protein peptide of the connective tissue is easily absorbed by the human body, and has functions of preventing and/or alleviating and/or treating related diseases. Further, the method includes operation steps that are simple and easy to perform, which has low energy consumption, appropriate and effective utilization of animal natural resources, as well as environmental friendly, non pollution of environment, and low production costs, which is suitable for large-scale industrial production, and the purpose of efficiently preparing an protein active peptide from connective tissue can be achieved.