In completeness theories of multiple-valued logic, the characterization of Sheffer functions is an important problem,and the solution can be reduced to determining the minimal coverings of precomplete categories. It’s well known that each precomplete set is a function set, ( )mT G , preserving the relation mG , therefore, the categorizing of this relation has provided the determination of precomplete set’s minimal covering with more convenient ways. In this paper, simply separable relations in partial four-valued logic are categorized by similar relation.