Abstract: This paper gives the proof that the crack stress intensity factors in the orthotropic elasic plate can be calculated by using the superposition principle, and illustrates the application of symmetry-skewsymmetry principle to the Griffith crack-tip stress intensity factors. K_Ⅰ and K_Ⅱ of the Griffith Cracks in the orthotropic plate for more than twenty loading conditions are calculated by the application of these two principles, and their general application formulae are also tabulated.