Objective： NK cell activity is related to degree of human immunity. Diabetes patients are immune-compromised, and not much is known about the NK cell activity in type 2 diabetes. The purpose of this study is to find out the difference in NK cell activity between type 2 diabetes patients and controls, and to investigate the association between NK cell activity and HbAlc and insulin resistance Methods： Forty-nine subjects were enrolled in this study, with 23 type 2 diabetes patients and 26 normal glucose tolerant controls. Anthropometric and biochemical parameters including age, gender, body mass index (BMI), fasting glucose, c-peptide, insulin, HbAlc, cholesterol, triglyceride, HDL and LDL cholesterol were assessed. Homeostatic model assessment (HOMA) was calculated for insulin resistance. NK cell activity was measured using a newly developed NK Vue^® Kit (ATgen, Seoul), which is a method of detecting and comparing interferon-gamma level only from NK cells. Results： NK cell activity was lower in type 2 diabetes patients compared to control subjects (1513.60 ± 1180.29 vs. 1883.68 ± 877.89, P-value = 0.216)， though without a statistical significance. Pearson correlation analysis showed no significant linear relationship between NK cell activity and insulin resistance (Correlation coefficient -0.054, p 0.715)，but demonstrated a significant inverse linear relationship with festing plasma glucose (Correlation coefficient -0.360, P 0.011) and HbAlc (Correlation coefficient -0.303, Z10.034). Conclusion： NK cell activity was lower in type 2 diabetes compared to controls, and NK cell activity was in significant inverse correlations with festing plasma glucose and HbAlc levels. A further, larger population study is warranted to confirm the possible correlation.