3’,5’-cyclic adenosine monophosphate (cAMP) is a key second messenger.It′s synthesis is strictly controlled.In this study, a genetically-modified yeast strain G2 in our lab was used for preliminary fermentation process optimization to improve extracellular cAMP production and investigate the key parameters.It showed that the most important parameters were the contents of glucose, yeast powder and peptone, and their ratio.The fermentation medium containing 100 g/L glucose and 2*YP (20 g/L yeast powder, 40 g/L peptone) led to the maximum cAMP concentration of (4 311.2±308.3) μmol/L, while the medium containing 100 g/L glucose and 1*YP produced cAMP (1 972.0±122.5) μmol/L.Adding precursor adenine to the forementioned media would further increase the cAMP concentration to (4 678.1±238.6) and (3 387.3±277.8) μmol/L, respectively.On the other hand, addition of precursor hypoxanthine led to the cAMP titer increase by 6.65% in the medium containing 100 g/L glucose and 1*YP.All of those results provided the clue for further optimization of fermentation process and modification of the cAMP-producing strains.