Objective: To design new and effective polyphenol oxidase （PPO） inhibitors and expand their application in the field of aquatic product preservation. Methods: The synthesized H₈[P₂Mo₁₇Ni（OH₂）O₆₁] （P₂Mo₁₇Ni） structure was characterized by ultraviolet and infrared spectrum. The inhibitory effect, type and mechanism of P₂Mo₁₇Ni on the relative activity of mushroom PPO in vitro was clarified. Then, the preservation effects of P₂Mo₁₇Ni on Litopenaeus vannamei Boone were evaluated through studying the index change of shrimps treated with P₂Mo₁₇Ni stored at 4 ℃, in which included the sensory score, the value of chromatic aberration L*, the value of total chromatic aberration （ΔE）, the total number of colonies, the value of pH and the value of total volatile basic nitrogen （TVB-N）. Results: The results showed that P₂Mo₁₇Ni was synthesized successfully. P₂Mo₁₇Ni inhibited the activity of PPO from mushroom in vitro with semi-inhibitory concentration （IC₅₀） of （0.377±0.004） mmol/L. P₂Mo₁₇Ni inhibited mushroom PPO in a competitive reversible manner, and the inhibition constant K_I was 0.185 mmol/L. Under the cold storage condition of 4 ℃, compared with the control group, P₂Mo₁₇Ni could effectively delay the decline of sensory score and the increase of L* and ΔE value in shrimps treated with P₂Mo₁₇Ni, and the inhibitory effect was significant. P₂Mo₁₇Ni could significantly inhibit the increase of total number of colonies, pH value and TVB-N value. P₂Mo₁₇Ni could extend the shelf life of shrimps for 4~5 days. Conclusion: P₂Mo₁₇Ni can slow down the blackening of shrimps and prevent its spoilage. P₂Mo₁₇Ni possesses a good preservation effect on L. vannamei and can be used in the preservation industry of aquatic products.