To study the regularity of mouse endostatin expression in B16 cells transfected by pEgr−ssEndostatin after different doses of X-ray irradiation and different time after the irradiation, mouse endostatin cDNA was amplified by RT−PCR and signal peptide was ligated to it. The pEgr−ssEndostatin recombinant plasmid was constructed and transfected into B16 cells with liposome and cells were irradiated. The expression of endostatin in the supernatant medium of B16 cells was detected by ELISA. The results showed that the cDNA sequence of mouse secretable endostatin is identical to the literatures. Egr−1 promoter and secretable endostatin cDNA were inserted into expression vectors correctly. pEgr−ssEndostatin had the expression property induced by radiation. It suggests that the Egr−1 promoter can be activated by ionizing irradiation and expression of downstream gene can be regulated.