Previous studies reported a close relationship between obesity and insulin resistance in the essential hypertensive patients. Objective In this study, we examined the relationship between the skin fold thickness and insulin resistance then developed a formula to estimate the insulin resistance index according to the skin fold thickness in the essential hypertensive patients. Subjects and Methods Medical records of 80 patients (37 males, 43 females) were reviewed and the data were tabulated. Anthropometric indexes (including height, weight, waist circumference, hip circumference, and skins fold thickness at 5 fatty difference points on the Erdheim diagram), fasting plasma glucose and insulin concentration were recorded. The mean age was 57.0±9.2 years. The insulin resistance index was calculated following the Homeostasis Model Assessment (HOMA) formula. Results Compared with the group with BMI＜23kg/m2, the group with BMI≥23 kg/m2 had higher fasting insulin concentration (8.85 ± 4.97 pmol/L vs 15.60 ± 8.70 pmol/L, P＜0.001 ) and higher insulin resistance index in (2.15±1,24 vs 3.76±2.22, P＜0.001). No significant difference in fasting plasma insulin concentration,insulin resistance index between male and female was observed (P＞0.05). There was a positive correlation between skin fold thickness and the fasting insulin concentration and insulin resistance index. The skin fold thickness at point A8 had the best coefficient correlated with fasting plasma insulin(r=0.79, P＜0.001) and insulin resistance index (r= 0.79, P ＜ 0.001). A formula to estimate the insulin resistance index by skin fold thickness at point A8 as: Insulin resistance index = 0.12 × [skin fold thickness at A8 point (mm)] - 1.Conclusion: In the essential hypertensive patients, the formula to estimate insulin resistance index as 0.12 × [skin fold thickness at A8 point (mm)]-1 may predict accurately the level of insulin resistance.