Objective: To study effect of overexpression of hypoxia-inducible factor-1 alpha induced by hyperoxia in vivo in LNCaP tumors on tumor growth rate. Methods: The prostate cancer LNCaP cells were inoculated in the abdomen of mice. All the mice were randomly placed in the gas chamber with different oxygen content. The groups were divided as follows: twelve mice in hypoxia group, sixteen mice in normoxia group, ten mice in hyperoxia group. After 28 d of treatment, the mice were weighed. the blood samples were taken from the left ventricle, and the tumor was isolated and weighed. Tumor growth. angiogenesis and vascularization, HIF-1 alpha expression and intracellular signal transduction molecules expression in each group of xenografts were detected and analyzed by using Western blotting and immunofluorescence and determination of hemoglobin. Results: Comparison of the growth of xenografts in each group showed that, the xenografts growth of hypoxia group was more quickly than that of normoxia group. The difference was statistically significant (P=0.004). The difference in xenografts growth between hyperoxia group compared and normoxia group was not statistically significant (P>0.05). The expressions of HIF-1 alpha, VEGF and VEGF-R of xenografts in hyperoxia group were significantly higher than those of normoxia group (P<0.05). The expression of HIF-1 alpha of xenografts in hypoxia group and normoxia group were similar. The blood growth rate of xenografts in hypoxia group (170%) was significantly higher than that of normoxia group (40%) (P<0.05). The expression of Nrf2 of xenografts in hyperoxia group was significantly higher than that of normoxia group (P<0.05). Conclusions: When hyperoxia induces the overexpression of HIF-1 alpha in LNCaP tumor, it will not affect tumor growth. It provides a new ideas and theoretical basis for the clinical treatment of prostate cancer.