In this paper, the plasmid stability and the concentration of recombinant E.coli DH5α were investigated by adding glucose of different concentration at the beginning of fermentation. The result shows that glucose was good for the growth of recombinant E.coli DH5α and the stability of plasmid. The optimal concentration of glucose was 1g/L. The biomass concentration could be up to110.930g/L and the fraction of plasmid-carrying cell was about 99% in the optimized culture medium.