In this study, firstly, real, complex and quaternion combinations of octonionic ma-trices are defined. In terms of these defined combinations, basic operations of oc-tonionic matrices are given. Later, algebraic structures of octonionic matrix set are obtained. In addition, the modulus structures of the octonionic matrix set on the real, complex and quaternion matrix sets are examined. Bases and dimension of oc-tonionic matrix sets with modulus structure have been found. Finally, special octon-ionic matrices and transpose, conjugate, trace of octonionic matrices are given.