Pullulan is an extracellular water soluble polysaccharide, which has been considered as a promising biodegradable material. And its derivatives have been of interest in past few years in a broad range of industrial fields including the food, cosmetics. The effects of culture pH ranging from 2.0 to 7.0 on cell growth, pullulan biosynthesis, the activity of pullulan-degrading enzyme, and the molecular weight of pullulan were investigated. The optimal pH for biomass formation was around 3.0, whereas the value for pullulan production was around 5.0. The portion of high molecular weight pullulan declined with fermentation time. In addition, when the pullulan-degrading enzyme was detected, its activity increased until the end of the fermentation, which caused the molecular weight to decrease faster, indicating that the pullulan-degrading enzyme was correlated with the decreasing molecular weight of pullulan. A dual-stage pH process that maximizes product formation has been successfully demonstrated with a high product yield of 78.12g/L with the relatively high average molecular weight of 2.02 × 10⁵Da.