Abstract: J115 and G161 are two strains of endophtic bacteria Enterobacter cloacae with strong associative nitrogen-fixing ability were isolated from rice stems and roots, respectively. The growth conditions of these bacteria were studied. The optimum time of culture for these bacteria was about 36 h and growth temperature was ranged from 27-30 C. Similarly, the optimum pH value of media was ranged from 6-7. The results showed that aeration or vibration culture (120 r min 1) was beneficial to the bacterial growth.