Abstract: Significant computation time is consumed to obtain a better solution for large functions.Decomposition conversion methods are proposed for canonical or-coincidence expansions.Transformation matrix is obtained between c_j maxterm and d_j maxterm expansions for canonical or-coincidence expansions.An efficient "inclusion" method is proposed using "AND" and "NOT" bitwise operations to simplify matrix operations.As a result,considerable reduction in time is achieved.Based on the "inclusion" methodology,on-set c_j maxterms are decomposed into different groups to achieve further time reduction by reusing duplication calculation in matrix operation.cj maxterm expansion and corresponding minterm expansion are used as inputs respectively.Experimental results show that the proposed decomposition methods achieve good performance for not only small variables but large variables as well in terms of conversion time.