Abstract: The criterion of statistical fracture for brittle materials under multi-axial stress is developed based on statistical fracture theory. In this criterion, the penny-shaped crack model is selected to simulate the defects in brittle material, the normal vector of the crack’s plan is used to describe the random direction of the crack’s plan in the material, and the effective stress is employed to represent the stress state. The criterion describes the relationship between the ultimate strength, stress state, failure probability and material’s property coefficients. According to the criterion, the following conclusions can be drawn: 1) Under multi-axial compressive stress states, the greater the confining pressure is, the greater the ultimate strength is; the greater the friction factor of the crack’s plan is, the greater the ultimate strength is; 2) The greater the volume stressed is, the less the ultimate strength is. Theses conclusions are consistent with current study results. The predicted results by this criterion are in good agreement with the test data.