Objective To construct the expression vector of early growth response-1 promoter-macrophage inflammatory protein 3? (pEgr-1-MIP-3?, pEM) to study MIP-3? expression in transfected Lewis lung cancer cells. Methods MIP-3? cDNA was inserted into plasmid with Egr-1 promoter by directional cloning. The vectors were transfected into Lewis lung cancer cells with liposomes. The expression of MIP-3? in transfected Lewis lung cancer cells induced by electron ray irradiation at different doses were confirmed by RT-PCR and Western blotting. Results The recombinant vector was sequenced, and the result indicated the correct insertion in the expression vector. After electron ray irradiation at different doses, MIP-3? expression in the transfected Lewis lung cancer cells increased significantly. Conclusion Electron ray can enhance the expression of MIP-3? in Lewis lung cancer cells. This has laid the experimental foundation for the studies of pEM for radio-genetic therapy in vivo.