Equisetin (EQST) belongs to polyketide (PKS)-nonribosomal peptide synthetase (NRPS) type compound with an inhibitory effect of 11β-hydroxysteroid dehydrogenase 1 (11β-HSD1) enzyme activity. This study investigated anti-obesity effect and insulin resistance improvement effect of EQST on high-fat diet (HFD)-induced ob/ob mice model. EQST treatment effectively reduced the body weight gain, fat weight gain and blood lipid content of model mice. All animal experiments were approved by the Medical Ethics Committee of Capital Institute of Pediatrics. EQST alleviated adipose tissue expansion and hepatic ballooning degeneration of model mice, and also effectively controlled the blood glucose content after glucose load and insulin load, showed a significant improvement in obesity and insulin resistance. EQST inhibited adipogenic proteins fatty acid-binding protein 4 (FABP4) and peroxisome proliferators-activated receptor γ (PPARγ), and upregulated thermogenic protein (uncoupling protein 1, UCP1) through suppressing 11β-HSD1 protein expression. In addition, EQST widely upregulates mitochondrial respiratory metabolism related proteins in adipose tissue and may improve insulin resistance through phosphatidylinositol-3-kinase (PI3K) pathway. Therefore, EQST plays an anti-obesity role by promoting adipose tissue thermogenesis and improving insulin resistance, which may provide reliable clues for improving obesity and diabetes.