Abstract: The inhibitory activity of IL一2 was determined in the serum of Lewis Iungtumor一bearing mice. The result showed that the inhibitory of IL-2 inthe serumof tumor一bearing mice was higher, and the level of activity was elevated with the tumor weight concomitntly.Bsides,the hyperplasia responsive effect of Con A activated the spleen cell in normal mice which influence by the serum of tumor一bearing mice was determined too,the relationship may be existed between the inhibitory activity of IL-2 and the inductive production level of IL-2 in the tumor-bearing mice were also discussed in this paper.