A model of percolation process named the multiple grain control percolation (MGCP) is proposed in order to estimate the connectivity of the melt phase in a partially molten rock in which spatial melt distribution is determined by the combination of surrounding grain species. According to the stability of the melt phase at the grain boundaries, three types of percolation model are introduced: the corner percolation, the edge percolation and the corner-edge (CE) percolation. The CE percolation can be reduced to the corner or edge percolation. The connectivity of the melt phase is determined as a function of modal composition in a multiphase grain system. For various combinations of grain species surrounding the corner or edge occupied by the melt phase, we obtain the critical grain fraction at which the connectivity changes abruptly from 0 to 1. The critical grain fraction estimated from the MGCP does not coincide with that from the ordinary percolation model in which random distribution of the melt phase is assumed. As a geophysical application of the MGCP, we construct the connectivity diagrams (modal composition diagram of the connectivity of the melt phase) for two partially molten peridotites by using the experimental results of dihedral angle measurements. From these diagrams, we predict that the melt phase is connected extensively if fraction of olivine exceeds 63 vol.% for a natural peridotite composed of olivine, orthopyroxene and clinopyroxene, and 38 vol.% for a synthetic peridotite composed of olivine and orthopyroxene. For the former peridotite, we further estimate critical melt fraction. It is shown that the melt phase can be connected extensively when the melt fraction exceeds 0.8 vol.% in the peridotite composed of more than 63 vol.% olivine. ¿ American Geophysical Union 1989