It is known that every completely -simple semigroup is isomorphic to a normalized Rees matrix semigroup over a - monoid. Utilizing this result, we show that the homomorphism of a completely -simple semigroup is a good homomorphism. Consequently, we give a construction theorem of homomorphisms between completely -simple semigroups. This result strengthens the one given by Ren et al in [8] on homomorphisms of completely -simple semigroups.