Abstract: To investigate the effects on physiological characteristics of tumor cell lines by space environment and inaugurate a new pathway of immune therapy in cancer, three tumor cell lines were carried in the returning module of spacecraft launched by Shenzhou-4 （SZ-4）. Three cell lines were returned after 7 days’ flying in space. All survival cells were monocoloned and the cell cycle, morphology, adhesive force and expression of cytokines were studied. The cell cycle of mouse melanoma B16 cells was changed after the flight. Comparing with the control group on the ground, the cell number of G1 phase was increased markedly （p ＜ 0.05）. With that simulta-neously, B16 cells showed multiple cell morphological changes. Adhesion to vascular endothelial cell was decreased in human lung carcinoma L78 cells, however, it was enhanced after passage for 2-3 times in L78 cells. The expression of cytokine IL-2, IL-8, TNF and TGF were improved in human cervical carcinoma Caski cells. In contrast, the expression of these cytokines was reduced in L78 cells. All these results revealed that physiological function of tumor cells were affected by the space environment. Whether the immunity was strengthened in tumor cell should be further studied.