Abstract: Based on Green function, Mirror inversion and pressure superposition principle, a semi-analytical model for pressure behavior analysis is established for volume fracturing in horizontal wells in fractured reservoirs with box-type closed boundaries. This model uses the classical Warren-Root model to show the seepage relationship between matrix and fracture and the spatial distribution of fracturing system in the volume fracturing regions, and takes the pressure interference of adjacent main fractures into consideration. So the reservoir seepage characteristics can be described better and the interpretation parameters are more consistent with the actual situation. The paper uses the model to analyze the sensibilities to parameters such as fracture number, fracture half-length, fracture interval, storage ratio and interporosity flow coefficient. The results show that the response process of bottom hole pressure can be divided into 6 flow stages based on the double logarithm curve chart, i.e., linear flow of artificial fracture, interporosity flow of dual medium, the first radial flow, the second linear flow, pseudo-state radial flow and closed boundary flow. Fracture number has significant influences on the whole response process—the larger the fracture number and the producing pressure drop are, the higher the single well deliverability will be. The growth of producing pressure drop decreases with the increase of the fracture number. There is an optimal economic value in a volume fracturing horizontal well. The single well deliverability and the producing pressure drop at the early production stage will increase with the increase of fracture half-length. If the fracture interval increases, the effective time of the first radial flow will increase and that of the second radial flow will decrease. At the late production stage, the larger the producing pressure drop is, the smaller the growth of the deliverability will be; the smaller the storage ratio is, the more obvious the fluid channeling will be; the smaller the interporosity flow coefficient is, the later the fluid channeling occurs