Petrogenetic grids of greenschist facies of metavolcanic and metavolcani- elastic rocks can be fundamentally represented by an assemblage of six phases of ternary system:. actinolite-biotite-calcite-chlorite-epidote-muscovite; and an- other assemblage of six phases of ternary system; albite-actinolite-biotite-calcite -chlorite-epidote, Generally quartz is an excess component. On the premise that the petrogenetic grids discussed possess dual similar intepsity variables. each assemblage of the six phases of ternary system has only a pair of petrogenetic grids. But the non-closed divariant fields of that pair of petrogenetic grids are similar. The slopes of boundaries (corresponding univariant curves) between non-closed divariant fields of the pair of petrogene- tic grids are of the same too. Also the arranged sequence of the non-closed divariant fields and corresponding univariant curves is the same. Therefore, the relationship between the petrogenetic grids of the pair may be considered as topological homomorphic transformation. The relationships between numbers of invariant points and univariant cur- ves, as well as, between numbers of invariant points and divariant fields in each petrpgenetic grid of six phases of ternary system, can be expressed by two equ- ations; u=i/2(11-i) (1) anmd d=i(9-i)/2+g+1 (2) where u=number of univariant curves; i=number of invariant points; d=num- ber of divariant fields; c=number of indifferent cross points. Besides, another notable point is in that, in the natural world the most widespread paragenetic mineral assemblages are generally of those in the non- cosed divariant fields of the petrogenetic grids.