Abstract: To investigate the fracture toughness of stainless steel sheet materials, compact tensile specimens were used for testing, and three methods for obtaining the plane stress fracture toughness were proposed and compared. The plane stress fracture toughness of the material was obtained by using the maximum force point, and constructing a univariate quartic polynomial model and a univariate cubic polynomial model of the relationship between the driving force load and the effective crack size. The results show that the plane stress fracture toughness obtained by the three methods was not significantly different.