By microbial enrichment culture method,bacteria including 9 strains of N fixing(A1 A9),7 strains of P releasing(B1 B7)and 6 strains of K releasing(C1 C6)were isolated from the rice paddy soil.Each strains capacity of N fixing or P releasing or K releasing and their combined effects on rice seedling growth were studied.The results showed that strain A5,B2 and C5 exhibited the best performance and they could be classified into Azotobacter,Pseudomonas and Bacillus specie,respectively.After culturing for 30 days,the balanced mixture of these three strains could increase total N content,soluble P and soluble K in the soil by 21.32%,32.17% and 45.57% respectively.Rice seedlings treated with combined bacteria culture had a better performance in plant height,fresh weight,dry weight and total plant N,P and K content compared to the control,which implies that the strains isolated in this study play an important role in transition of N,P and K nutrients in the rice paddy.