The invention discloses a non-orthogonal natural crack opening judgment method under a hydraulic fracturing temporary plugging condition. The method sequentially comprises the following steps that A,establishing a crack expansion physical model under the temporary plugging condition; B, integrating a fluid pressure drop equation, a substance balance equation and a flow boundary condition to establish an in-crack fluid flow model; C, calculating a crack overall induced stress field by adopting an improved displacement discontinuity method and determining crack stress boundary conditions; D, obtaining fluid pressure and crack width distribution according to the in-crack fluid flow model, the crack induced stress field model and corresponding boundary conditions, and judging whether the rockmass meets damage conditions or not; and E, respectively judging the opening condition of the natural crack according to the natural crack opening criterion under the temporary plugging condition. According to the established judgment method, the influence of hydraulic fracture induced stress on the natural fracture opening process is fully considered, judgment conditions are established for natural fractures distributed on the two sides of the hydraulic fracture, and the judgment conditions better conform to the actual situation.