Abstract: Objective: To study the platelet activation in patients with malignant tumor and the clinical value of detection of CD62p and CD63 in the patients. Methods: Flow cytometry was used to detect the expression of platelet activation markers CD62p and CD63 in 76 cancer patients (45 cases without metastasis and 31 cases with metastasis) and the results were compared with the normal control group. Results: The expression of CD62p and CD63 in cancer patients was significantly higher than that of the controls (P<0.01). The expression of CD62p and CD63 in metastasis group was significantly higher than that of the non- metastasis group. Conclusion: The platelets in cancer patients are activated. The level of activation is associated with the occurrence of metastasis.