The method for preparing oligopeptide (number of amino acids contains by peptide is less than 10) by enzymolysis of pork skin collagen is mainly technically characterized by that it uses pork skin collagen as raw material, under the condition of gradually changed pH value without addition of alkali it utilizes the synergistic hydrolysis action of acid protease, alkaline protease or/and neutral protease to obtain oligopeptide. The pork skin raw material for enzymolysis is fresh pork skin, the protease synergistic action hydrolysis condition is: temp. is 30-70 deg.C, time is 2-12 hr, and the substrate concentration is 20-100 g/l. Said invention has no need of adding alkaline solution in hydrolysate in the course of whole hydrolysis, can simplify downstream process and is favorable for reducing production cost of oligopeptide.