An element initial stress method to calculate stress intensity factor of three-dimensional mixed-mode crack was introduced, which adopted the degradation of the 1 / 4 node singular element to get the stress intensity factor from calculating the stress of the prime point stress about the crack tip When a cylinder buried inside the circular ramp crack under far-field equal tensile force was calculated by this method, compared with exact solutions, the relative error of the stress intensity factor numerical solution, the maximum relative error of KI was 1.44 percent. the maximum relative error of KⅡ was -2.30 percent. the maximum relative error of KⅢ was -1.22 percent. This method was worth promoting, because it was more exact, simple and propitious to calculate the stress intensity factor of mixed-mode three-dimensional crack problems.
