Abstract: A strain of rhodopseudomonas sp synthesizing 5-aminolevulinic acid was screened and the affecting factors for biosynthesis were investigated. The experiment results showed that the culture with light and no oxygen was the best culture mode for the production of 5-aminolevulinic acid. Sodium glutamate was the best carbon source and yeast extract was the best nitrogen source for the strain. According to the results of orthogonal design test，the optimal culture medium for the production of 5-aminolevulinic acid was decided. The best concentration of sodium glutamate was 2.0 g • L－1. The best concentration of yeast extract was 1.5 g • L－1. The best inoculum size was 30%，The best pH was 7.0. The experiment results showed that the production of 5-aminolevulinic acid could be increased greatly as compared with literature. Under this optimal conditions，the production of 5-aminolevulinic acid by this strain was as high as 49.39 mg • L－1.