Abstract: Bacillus amyloliquefaciens BG-09 was used as the starting strain to analyze the gene psd related to cell membrane permeability in metabolic pathways,and to investigate the effect of over-expression of gene psd on cytidine fermentation. The psd was cloned using the B. amyloliquefaciens BG-09 genome as a template,and the recombinant plasmid pHT43-psd was constructed by ligating it with the vector pHT43.The recombinant plasmid was transformed into the strain E.coli DH5α by chemical transformation. After successful verification,it was transformed into B. amyloliquefaciens BG-09 by electroporation and the recombinant strain B. amyloliquefaciens BG-09-psd was obtained. The successfully constructed B. amyloliquefaciens BG-09-psd strain was fermented in shake flasks to study the effects of overexpression of the gene psd on cell growth,cytidine and uridine production accumulation. The results showed that the concentration of cytidine in the fermentation broth of recombinant strain B. amyloliquefaciens BG-09-psd was 1.199 g/L,with an increase of 15.51% compared to the control strain B. amyloliquefaciens BG-09,and the concentration of uridine was 0.552 g/L,which increased by 6.56%. This showed that over-expression of gene psd could promote the accumulation of cytidine.