Objective To study the effects of pioglitazone (PGZ) on the expressions of 11β-hydroxys-teroid dehydrogenase type 1(11β-HSD1) in central nervous system of diabetic rats and its asociation with cog-nitive function. Methods Thirty male SD rats were equally randomized into Control group (C group)，Diabetic group (D group) and Diabetes+Pioglitazone group (DP group). Morris-water maze was used to test the cognitive function after 8 weeks. Western Blot was used to detect the expressions of 11β-HSD1 in hippocampus and hy-pothalamus. Results In Morris water maze，the number of crossing the platform in D group were significantly less than C group and DP group (P ＜0.01). The 11β-HSD1 expressions in hippocampus and hypothalamus of D group were significantly increased than C group and DP group，while the 11β-HSD1 expressions of DP group were significantly increased than C group (P ＜0.01). Conclusion Pioglitazone may improve cognitive function in diabetic rats，partly through the decrease of 11β-HSD1 expressions in hippocampus and hypothalamus.