Aim To observe the effect of high glucose on the expression and activity of thrombomodulin in human umbilical vein endothelial cells （HUVEC）. Methods HUVEC were incubated in vitro, sub-experiment: ①control group ②10 mmol/L glucose group ③20 mmol/L glucose group, all incubated for 24 h. Flow cytometric and RT-PCR technique were used for detecting thrombomodulin protein and mRNA, respectively. Microplate Reader was used for detecting thrombomodulin activity. Results Compared with control group, both mRNA （2.05±0.19、1.44±0.32 vs 1）and protein （41.38±3.41、32.60±2.59 vs 27.96±1.58） levels of thrombomodulin increased in 20 mmol/L glucose group and 10 mmol/L glucose group （P<0.05） and the thrombomodulin activity enhanced （0.4157±0.0129 vs 0.3957±0.0100，P<0.05） in HUVEC of 20 mmol/L glucose group. Conclusion Exposure to high glucose increased the expression of thrombomodulin and enhanced the thrombomodulin activity in HUVEC. The upregulation of thrombomodulin in HUVEC cultivated in high glucose conditions may represent a defense mechanism against the stress.