Abstract: Objective:To explore the significane of changes in the quantity of platelet α-granule menbrane protein-140(GMP-140) in patients with rheumatoid arthritis(RA).Methods:The quantity of platelet GMP-140 in plasma were detected by ELISA in 42 cases of RA and 15 normal controls. The blood platelet count(BPC) and erythrocyte sedimentation rate(ESR) were measure too.Results:The quantity of plasma platelet GMP-140 (58 32±8 18ug/L, n=24) in active RA group was significantly higher than that in remissive RA group (17 18±2 58ug/L, n=18) and normal controls (15.74±2.33ug/L,n=15), (P0 001 and 0 001). There was no significancy difference between remissive RA group and normal controls (P0 05). The level of plasma platelet GMP-140 in 15 cases of active RA was obsered before or after treatment. After treatment, the plasma platelet GMP-140 had obviously reduced. There was a correlation between a level of plasma platelet GMP-140 and BPC(r=0.797, P0 01), and also acorretation between a level of plasma platelet GNP-140 and ESR(r=0 459,P0 05).Conclusion:The patients of RA had not only changes of platelet quantify, but also platelet activation.There was correlation between paltelet activation and activty of disease,and may be a second change.In clinic,the treatment of RA is key the preventing platelet activation and thrombosis formation.