The invention relates to a modeling method for a compact sandstone reservoir three-dimensional fracability model. The method comprises the following steps: S1, establishing a relation formula among an internal friction angle, I type and II type crack fracture toughness and the parameter of sandstone mechanical characteristics; S2, establishing a shale fracability evaluation model which comprehensively considers an elastic parameter, the internal friction angle, the critical strain energy release rate and fracture toughness; S3, adopting a support vector machine algorithm to obtain a cluster analysis mode between the reservoir fracability and the elastic parameter; S4, adopting the cluster analysis mode to obtain a reservoir three-dimensional elastic parameter data body, and establishing the multi-scale compact sandstone reservoir three-dimensional fracability evaluation model based on the core, the borehole and the reservoir of multiple scales. According to the method, the fracability of an arbitrary space position in the compact sandstone reservoir can be obtained, a sweet spot with high fracability can always be drilled when drilling a compact sandstone gas well, blindness of well location selection is avoided, and the fracture modification effect and the yield after fracture are improved.