Abstract: Five endophytic diazotrophs with high and stable nitrogenase activity screened from Guangdong bamboo(B am busa blum eana J. A. et J. H. Schult. f. )were studied by physiological test, the adap tability to environmentsand the growth-p romoting effects on rice. The results showed that these strains could grow well at 18—40 ℃and hadnitrogenase activity at 26—37 ℃for op timum growth under nitrogen-free medium. Strains also showed nitrogenaseactivity at a pH range of 5. 0 to 8. 0, at a saline (NaCl) concentration range of 0. 5—2. 5 g·L -1 and at a range of0. 05—0. 50 g·L -1 (NH4 ) 2 SO4. Strains can secrete acid or alkali substance as neutralizer at pH 8. 0 and 5. 0 respectively. Experiments of inoculation on rice showed that strains had obviously effects on p romoting the growth ofp lants.