Abstract: Volume fracturing is the key technology for improving production of tight sand oil reservoir. By the approach of integrating finite element method with discrete element method, a model for fracture propagation by volume fracturing process is developed in this paper, by which the fracture propagation modeling of multiple clusters fracturing of horizontal well in Chang?7 tight sand oil reservoir of Changqing oilfield is researched. The result shows that volume fracture could easily form when stress difference is lower than 4 MPa, and planar fracture mainly formed when it is higher than 5 MPa. The density of natural fracture could only affect the stimulation effect when the stress difference is very low. When the stress difference is 3 MPa, the interference of fracture between clusters is serious and partial merge of fractures will appear. In this situation, no matter increasing number of perforation cluster or reducing cluster space, the stimulating reservoir area won’t increase obviously. When the stress difference is 5 MPa, the interference of fracture between clusters is weak. Increasing number of perforation cluster is beneficial for hydraulic fractures to connect with more natural fractures, improving the development degree of the volume fractures and expanding the stimulation area.