The water sorption kinetics of fermented biscuits with different porosity and fat content were determined using dynamic moisture adsorption methods at 25℃. The moisture sorption isothermal and effective moisture diffusion coefficient were obtained based on GAB model and infinite slab model. The results showed that the porosity had almost no effect on equilibrium moisture content of biscuits,while as the fat content increased,the equilibrium water content gradually decreased. GAB model was suitable for fitting the sorption data of biscuits. Effective moisture diffusion coefficient reached a maximum with water content increasing and then decreased to a constant value. The maximum of effective diffusion coefficient was reached at the moisture content of 10 g /100 g dry basis. The maximum of effective moisture diffusion coefficients of fermented biscuits with porosity of 87%,76% and 68% were 7. 8 × 10- 10m2/ s,5. 6 × 10- 10m2/ s and 3. 4 × 10- 10m2/ s respectively,which were mainly related to the mechanism of moisture diffusion,i. e. vapor water diffusion in pores was changed to liquid water diffusion in the solid matrix. Increasing fat content significantly decreased moisture diffusion coefficient. Results showed that the effective diffusion coefficient decreased from the maximum value of 5. 6 × 10- 10m2/ s to 2. 3 × 10- 10m2/ s.