Objective To analyze the correlation between body mass index (BMI) and all-cause mortality in the retired military cadres from the Second Military Medical University. Methods Clinical data of 237 retired military cadres hospitalized in our department from January 2000 to October 2013 were collected, and they were followed up until October 31, 2014. They were divided into 4 groups according to their BMI, that is, low body mass group (BMI＜20kg/m2), ideal body mass group (BMI 20.0?24.9kg/m2), overweight group (BMI 25.0?27.9kg/m2) and obesity group (BMI ≥28kg/m2). Cox regression analysis was used to investigate the all-cause mortality risks in the groups. Results The cohort of retired cadres were followed up for a median duration of 59 months, and no one was lost. All-cause mortality was 115 subjects when the follow-up ended. Cox regression analysis indicated that the all-cause mortality was decreased by 53.6% in ideal body mass group (HR＝0.464, 95%CI: 0.239?0.901, P＜0.05), 65.2% in overweight group (HR＝0.348, 95%CI: 0.162?0.749, P＜0.05) and 74.2% in obesity group (HR＝0.258, 95%CI: 0.103?0.644, P＜0.05) when compared with low body mass group after adjustments for confounders. Conclusion The increase of BMI is associated with the decreased risk of all-cause death in the retired military cadres.