Abstract: In recent years, the strategy of transport system modification has been widely employed for the development of amino acid production strains.In the present study, the industrial production strain Escherichia coli MT-01/p Trp-01 was chose as the start strain, the L-tryptophan uptake gene of mtr knockout mutant strain were built by the method of Red homologous recombination, the fermentation results of the mtr mutant showed that the production of tryptophan was 35.87 g/L, which was32% higher than that of the origin strain.Furthermore, the L-tryptophan excretion gene of ydd G was overexpressed at different levels by fusing with three different promoter ( Pr, Ptac and Pser A) , and the L-tryptophan yield and the cell growth of gene ydd G overexpression mutants were studied.The fermentation results showed that the ydd G overexpression mutant fused with the constitutive promoter of tac increased the production of L-tryptophan to 41.01 g/L, which was 14.3% higher than that of the gene mtr knockout strain, the yddg overexpression mutant driven by the temperature inducible promoter Pr produced 39.22 g/L L-tryptophan, which was 9.3% higher than that of the gene mtr knockout strain. However, the yddg overexpression mutant driven by the promoter ser A only produced 27.1 g/L L-tryptophan, and the cell growth of strain got significantly restrained.To sum up, overexpression of gene ydd G and knockout of gene mtr are beneficial to improve the ability of engineering strains to produce L-tryptophan.