Acid phosphatase(ACP) is a key enzyme involved in the degradation of flavorful substances inosinic acid (IMP). Therefore， inhibition of ACP is very important to maintain the flavor of aquatic products during storage. This study investigated the interaction and inhibitory mechanisms of epicatechin (EC) on ACP by UV-Vis absorption spectroscopy， fluorescence spectroscopy， circular dichroism and molecular docking. The results showed that EC could effectively inhibit ACP activity， and the IC50 value was 0.184 mmol/L. It was reversible inhibitor of ACP， and the inhibition mechanism was the un-competitive type by kinetic analysis. The inhibition constant (Ki) was 1.025 mmol/L when the concentration of EC was 0.1 mmol/L. The fluorescence of ACP was quenched by the interaction with EC and the quenching mode was dynamic quenching. The binding constant (Ka) of ACP was 1.455×105 L/mol after adding EC at 298 K. The interaction of ACP with EC was driven by hydrogen bonds and van der Waals forces. EC altered the secondary structure of ACP， resulting in an increase in α-helix and a decrease in β-folding， β-turning and random coil. This study provides a new idea to inhibit the degradation of IMP in aquatic products during storage.