The relationship between Fas apoptosis inhibitory molecule FAIM 1 and simple obesity was studied by using the blood of obese patients and the model of obese rats to provide the new experimental basis for revealing the molecular mechanism of obesity and the diagnosis and treatment for obesity. The correlation between FAIM 1 expression and simple obesity was determined through testing the expression of FAIM 1 protein in white blood cells for 17 cases of normal individuals and 40 cases of obese patients. To further reveal the relationship between FAIM1 and the occurrence and development of simple obesity, the model of obese rats was established by using high-fat diet, and the body weight and blood glucose levels of obese and control rats were measured. The successfully constructed obese model rats and normal rats were fasted for 12 hours. Blood taken from heart were used to measure the change of total cholesterol (TC), triglyceride (TG), high density lipoprotein-cholesterol (HDL-C) and low density lipoprotein-cholesterol (LDL-C) after anesthetizing animals. The epididymal fat pad and perirenal fat weights of obese rats and control rats were analyzed. The expression changes of FAIM 1 and insulin receptor beta (IR β) protein were detected by Western blot. The results showed the expression of FAIM1 protein in white blood cells of patients with simple obesity was reduced by 36.4% compared with normal control. Compared with the normal control rats, the serum levels of TC, TG and LDL-C in the obese model group were respectively increased by 37.1%, 25.6% and 39.1%, while HDL-C was reduced by 33.3%. The epididymal fat pad and perirenal fat weights of the obese model rats were respectively 1.85- and 2.24-fold of that in the normal control rats. Compared with the control group, the expression of FAIM 1 and IR β in the liver of obese rats were decreased by 45.9% and 32.6%, respectively, which was consistent with the results of clinical blood samples. So it displayed that the expression of FAIM 1 is significantly nagtively correlated with simple obesity, and FAIM 1 may be a new target for diagnosis and treatment for simple obesity.