objective: to explore the effects of saturated fats diets,polyunsaturated fats diets and monounsaturated fats diets on the expression of x-box binding protein 1(xbp-1)in liver tissues of rats. methods:wistar rats(n=48)were randomly divided into normal control group(n),saturated fatty acid diets group(s),monounsaturated fatty acid diets group(m),polyunsaturated fatty acid diets group (p). the rats in group n were fed with a regular lower fatty acids diet containing 10.3% fat,24.2% protein,and 65.5% carbohydrate as percentage of total calories. the rats in group m,p and s were fed with regular diets mixed with 15% tea oil,soybean oil,lard oil respectively,containing 35.4% fat,17.4% protein and 47.2% carbohydrate as percentages of total calories. the blood sample was collected by cardiac puncture after rats were anesthetized with diethyl ether for the biochemical analysis,insulin resistance was evaluated by glucose infusion rate (gir) of hyperinsulinemic euglycemic clamp technique. after 8 weeks,the rats were killed with phenobarbital sodium after hyperinsulinemic euglycemic clamp test,hepatic xbp-1 were detected by western blot and immunohistochemistry. results:① compared with group n,the amounts of food intake were significantly lower in group s,m and p(p < 0.05). adjusted for the amount of food intake,serum tc,tg in group s were significantly higher than group n(p < 0.05),but there was no detectable difference among n,p and m groups(p > 0.05). compared with group n,fins and fbg were significantly higher in group s and p groups(p < 0.05),gir was significantly lower in s,p and m groups(p < 0.05). ②immunohistochemistry analysis showed positive xbp-1 localized in both cytoblast and cytoplasm with intense brown staining. further more,western blot for xbp-1 in liver tissues showed that xbp-1 protein levels increased in group p and s [(1.09±0.16),(1.15±0.21)]compared with group n and m [(0.85±0.15),(0.79±0.14),p < 0.05]. conclusion:it may be one of the mechanisms of insulin resistance that the higher expression of xbp-1 and in liver tissues induced by polyunsaturated fatty acid and saturated fatty acid diets,simultaneously,it suggested that endoplasmic reticulum stress(ers)can be a core mechanism involved in triggering insulin resistance.