Abstract: Deep shale gas is mainly developed by cutting fracturing technology. However, the fracturing effect evaluation method based on microseismic event monitoring for calculating stimulated reservoir volume (SRV) is only suitable for volume fracturing of shale gas wells in medium and deep formations, and it is not applicable for evaluating the tight cutting fracturing effectiveness of deep shale gas wells. Therefore, a model for estimating the area of complex fracture network based on the octree grid was established to evaluate the effectiveness of tight cutting fracturing in deep shale gas wells by estimating the complex fracture network area. This model decomposes microseismic events into octree grids and a three-dimensional complex fracture network area equivalent model based on the grid equivalent area method was constructed, by which the area of fracture network can be efficiently estimated without reconstructing the fracture network. In order to quantitatively evaluate the calculation error of this model, a set of synthetic microseismic event point generation methods based on the Gaussian mixture model was established. The simulation results show that this method has high calculation efficiency and estimation accuracy. Field application examples show that compared with the traditional SRV evaluation method, the method can more accurately evaluate the effectiveness of tight cutting fracturing in deep shale gas wells.