Puts forward the concept of orthogonal (P,Q)- symmetric matrix, and the structure was constructed through the orthogonal projection.According to the orthogonal invariance of orthogonal (P, Q) - symmetric matrix,The problem was converted to solve orthogonal solutions of matrix equations by adopting direct substitution method. Applying the orthogonal triangular decomposition for matrix , necessary and sufficient conditions were derived and the general expression was gotten for the orthogonal solution to the matrix equations. The necessary and sufficient conditions were derived and the general expression was put forward for the orthogonal (P,Q)-symmetric solution to the matrix equation AX=B.