【Objective】 To explore the expression of USP9X in platelets and its effect on platelet function. 【Methods】 The expression of USP9X in human and mouse was evaluated by PCR and Western blot. Platelets from young and old mice were separated and prepared, and the expression of USP9X was detected. USP9X inhibitos were used to assess the regulation of USP9X in platelet function, including aggregation, ATP release and spreading. Platelet lysates were collected in different time points to evaluate the change of phosphorylation of Akt in USP9X inhibitors treated platelets. 【Results】 Both human and mouse platelets expressed USP9X. Compared to the young mice, the old mice showed significantly enhanced expression of USP9X(P<0.05). To assess the effect of USP9X on platelet function, USP9X inhibitor was used to pre-incubate platelets for 30 min and platelet function were examined later. Results showed that USP9X inhibitor significantly decreased platelet activation including aggregation, ATP release and spreading(P<0.05). Compared to the control group, the inhibitor treated group showed a significant decrease in the spreading area after 45 minutes. The Western blot results showed a significant decrease in Akt phosphorylation levels of platelets in the USP9X inhibitor treated group. 【Conclusion】 Both human and mouse platelet express USP9X, and inhibition of USP9X decreased platelet function including aggregation, ATP release and spreading. USP9X can also influence the phosphorylation of Akt. The inhibitor of USP9X may become a potential therapeutic target for thrombosis intervention.