[Objective] The aim was to construct threonine-producing strain M122 overexpressing key gene rhtB for transporter protein to transport threonine to the extracellular, and to investigate effects of different carbon or nitrogen sources and pH values on L-threonine production caused by the recombinant strain. [Method] The fermentation process of L-threonine-producing strain was analyzed by different carbon or nitrogen sources, and carbon or nitrogen sources and pH in fermentation medium were also optimized in this study. [Result] After direct modification, the uti- lization efficiency of threonine-producing strain on nutrients increases. When sucrose was used as carbon source for fermentation, Lothreonine yield via shaking culture was 28.1 g/L When （NH4）2SO4 or yeast powder was used as nitrogen source for fermenta- tion, L-threonine yield was 27.8 and 28.2 g/L respectively, which were all higher than that of other nitrogen sources. The study on optimal pH value showed that it was more beneficial for strain growth and L-threonine yield on neutral condition. [Conclusion] The best carbon source for threonine-produing strain M122 was sucrose, while the best nitrogen source was （NH4）2804 or yeast powder, and the most suit- able pH value was 7.0.
