Abstract: A mathematical model that described the strains growth, product formation and medium consumption was presented to predict the performance of batch fermentation of Zoogloea sp.GY3 which was screened from activated sludge and could synthesize PHAs.A simple model was proposed by using the Logistic equation for growth, the Luedeking-Piret equation for PHAs production and the Luedeking-Piret-like equation for sucrose consumption.The model appeared to provide a reasonable description for each parameter during the growth phase.The production of PHAs was growth-associated.The models were in good agreement with the measured data in experiments.