Fracture conductivity varying over time is one of the important factors influencing the fracturing well productivity. In order to study the fracturing well productivity of low permeability reservoir at sea, a productivity model of fracturing well was established on the basis of the infinite formation pressure drop formula, using the potential superposition principle and considering fracture conductivity changing over time. Studies on fracturing well productivity were performed using the established model. Results show that fracture conductivity changing over time has great impact on productivity, and fracturing well production law better fits reality using the new model. Finally, productivity impact factors were analyzed. Results show that the lower permeability the greater impact on productivity by fracture length, and the less impact on productivity by fracture conductivity. In lower permeability reservoir with smaller effective thickness at sea, more fracturing is needed to increase drainage area, enhance well productivity and improve economic benefits.