Abstract: The effects of ethephon on immunity in mice was investigated.The assay on plaque forming cell (PFC) of spleen, content of serum hemolysin, delayed hypersensitivity and macrophage function were carried out. The results showed that the thickness of footput, the numbers of plaque forming cell and the serum HC50 of mice,when treated with ethephon at 67~ 268 mg/kg bw, were significantly lower than those in the control group(P＜0.05,P＜0.01),and the macrophagocye index was lower than that in the control group at 268 mg/kg bw dose level(P<0.05).The results suggested that there were inhibitive effects of ethephon on immunity in mice.