Abstract: Traditional methods mainly focus on using microseismic events to calculate the stimulated reservoir volume (SRV). Currently, there is no effective method to estimate the stimulated reservoir area (SRA) of complex fracture networks for deep shale close-spaced volume fracturing. For this reason, this paper proposes an estimation model of SRA based on octree decomposition. This model decomposes microseismic events into octree grids and constructs a three-dimensional complex fracture network area equivalent method based on the grid equivalent area method. It could obtain the estimation of SRA efficiently without fracture network reconstruction. Besides, this paper also proposes a synthetic events generating method based on Gaussian mixture model to quantitatively evaluate the estimation error of SRA model. The simulation results indicate that the SRA model has good computational efficiency and estimation accuracy. The application examples also show that the SRA model proposed in this paper can more finely characterize the fracturing effect of shale compared with conventional SRV model.