Objective To investigate the roles of proinflammatory factors, including tumor necrosis factor-alpha(TNF-α), interleukin-1(IL-1) and IL-6 in the infectious multiple organ injury in aged rats. Methods Male SD rats were randomly divided into young control group (YCG, n=10), young model group(YMG, n=15), elderly control group (ACG, n=10) and elderly model group(AMG, n=25). Multiple organ injury was induced by injection of Klebsiella pneumoniae through tracheal intubation in rat models of pneumonia. The pathological changes of lungs, heart, kidneys, and small intestine were investigated immunohistochemically. The changes of proinflammatory factors expression in these tissues were also observed. Results The expression levels of TNF-α, IL-1, and IL-6 in lungs, heart, kidneys and small intestine were significantly higher in YMG and AMG than in YCG and ACG(P＜0.01 or P＜0.05). The pathological changes of lungs, heart, kidney and small intestine were more obvious in YMG and AMG than in YCG and ACG(P＜0.01 or P＜0.05). The expression levels of IL-1 in lungs, TNF-α and IL-6 in heart, and IL-1 and IL-6 in small intestine were significantly elevated, and organ injuries were severer in ACG than in YCG (P＜0.01 or P＜0.05). Conclusion Proinflammatory factors, including TNF-α, IL-1 and IL-6, play important roles in the development of infectious multiple organ injury in the aged rats.