【Abstract】Objective To study the effects of nitric oxide (NO) on the growth and metastasis of tumor.Methods The literatures of recent years were reviewed.Results NO had double effects on the growth and metastasis of tumor. NO promoted the growth and metastasis by regulating the expression of tumor proliferation gene and inducing tumor angiogenesis. On the other hand, NO had antitumor effects by interfering with the metabolism of tumor cells, inducing the damage of DNA, forming high toxic free radical, inducing apoptosis of tumor cells and mediating the antitumor action of endothelial cells and macrophages.Conclusion Selective blockage or induction of synthesis of NO may be a new way for tumor therapy.