Objective To investigate the possibility to use 3R(replacement,reduction,refinement) method in anti-tumor drug screening.Methods(1) The KM mice were inoculated with S-(180),H-(22) and EAC tumors to establish "three-tumors in one" model;(2) 1/3 KM mice were inoculated with S-(180),1/3 KM mice were inoculated with H-(22),the others were inoculated with EAC,to establish "one-tumor in one" model.The "three-tumors in one" model and the "one-tumor in one" model mice were infused with the anti-tumor drug per os,to observe the effect on the ratio of tumor inhibition and immune function.Results(1)The tumor growed slower in the "three-tumors in one" model mice than in "one-tumor in one" model,but there was no influence on the judgment of the drug's tumor-inhibition function.(2) The "three-tumors in one" model was very close to the "one-tumor in one "model in immunological parameter such as thymus,spleen,DTH,phagocytic and clearing indices.Conclusion The "three-tumors in one" model can be used to tumor inhibition and immune function experiments of the anti-tumor drug screening.