Objective To observe the correlation between platelet parameters , platelet activation marker and carotid intima-media thickness (CIMT) in patients with type 2 diabetes mellitus. Methods One hundred and ninety-five type 2 diabetic patients were enrolled in this study. The patients were divided into the normal control group, the CIMT increased group and the clot group according to the carotid intima-media thickness. Levels of platelet count (PLT), mean platelet volume (MPV), platelet distribution width (PDW), platelet hematocrit(PCT), urinary 11-dehydro-thromboxane B2 (11-DH-TXB2) and other clinical, biochemical characteristics were measured. Results (1) Levels of serum LDL-C, MPV, PDW, urinary 11-DH-TXB2 and clinical course in the clot group were higher than those in the CIMT increased group and the normal control group (P < 0.05). (2) Compared with the normal control group, the clinical course, serum LDL-C, MPV, PDW and urinary 11-DH-TXB2 were higher in the CIMT increased group (P < 0.05). (3) By using with spearman rank correlation test, carotid intima-media thickness was positively associated with age , course , BMI , GLU , GHbA1C , LDL-C , MPV , PDW and urinary 11-DH-TXB2, whereas carotid intima-media thickness was negative associated with HDL-C, PLT (both P < 0.05). (4) MPV, PDW and urinary11-DH-TXB2 were shown as the independent risk factors for CIMT. Conclusions Platelet activation marker and platelet parameters are associated with carotid intima-media thickness in patients with type 2 diabetes mellitus.