Abstract: Objective To investigate the tumor inhibitory effects of E838 and the combined antitumor effects of E838 and 137Cs γ-ray irradiation. Methods IRM-2 mice transplanted with 2～3mm3 lymphoma(LM) tissue for 24h, were randomized into nine groups: control group, radiation group, high、middle、low E838 dose group, different dose E838 combined with radiation group and cyclophosphamide group. E838 group and combined group administered with same dose E838 daily for 7 days, cyclophosphamide group administered every other day 4 times. Combined group radiated with 1 Gy/day for 5 days after the mice wereadministered with E838 for 4 days.The size of LM tumor and the bone marrow cells of different group were measured. Results The mouse LM tumor inhibitory ratios of three E838 doses groups were (44.14±15.96)%、(70.74±11.17)% and (50.00±18.09)% respectively. There was a significant difference between E838 groups and control group (P<0.001).The level of bone marrow cells counting was markedly elevated. E838 combined with 137Csγ-ray could enhance tumor inhibitory effect, the tumor inhibitory ratios of three combined groups were (65.43±2.13)%、(77.13±6.38)% and (67.55±11.17)%, there were obviously increased compare with control and radiation group respectively (P<0.001)． Conclusion E838 has good tumor inhibitory effects on lymphoma transplanted mice tumor. The synergistic antitumor effects was found after the mice were treated with E838 and γ-ray irradiation, the bone marrow function recovery after irradiation was speed up when the mice were administrate with E838 of some definite doses.