Objective To investigate the effects of inflammatory factors, lipid metabolism, and glucose metabolism on weight in the northern pig-tailed macaques in acute stage of SIVmac239 infection. Methods The levels of inflammatory factor (TNF-α, IL-6), lipid metabolism (cholesterol, triglyceride, high-density-lipoprotein cholesterol, and low-density-lipoprotein cholesterol), and glucose metabolism parameters (insulin, insulin resistance index) were analyzed and compared between the weight increase group and the weight decrease group in the northern pig-tailed macaque in acute stage of SIVmac239 infection. Pearson’s correlation analysis was used to investigate the correlation of plasma viral load and insulin resistance. Results There was no difference of plasma lipid level and inflammatory factors between the weight increase group and the weight decrease group in the acute stage of SIVmac239 infection. After SIV infection, the insulin levels decreased in the weight increase group. In the weight decrease group, insulin levels were significantly elevated and insulin resistance appeared. Pearson’s analysis showed that changes of insulin resistance index at the 5^th week and 11^th week after infection were positively correlated with plasma viral load. Conclusion In the acute stage of SIVmac239 infection,abnormal glucose metabolism is the main cause of body weight change in northern pig-tailed macaques.