The growth and interaction of Gluconobacter axydans and Bacillus megaterium in Vc two step fermentation have been studied. The results showed that there is a kind of coordinate symbiosis between G. axydans and B. megaterium during the fermentation, which could promoted 2-Keto-L-gulonic acid (2KGA) synthesis. The efficiency on the synbiosis would vary as the conditions of fermentation were different and were improved by the environmental factors.