The paper discusses the inherent factors and physicochemical condition of silicate Liquid.immiscibility.It suggests that Gexcess>0 in magma is internal reason of immiscibility, rich P2O5, TiO2, REtE, Zr, Ta, etc.in magma are induce- ments.The calculation of chemical potentials shows that ocelli-matrix from ocellar Bi-Py-syenite and syenitic and pyroxenitic magma unit had been equi- librated in liquid state, Yang Yuan magma immiscibility could occur in upper crust and at 1200℃ under reasonable geological condition. Two immiscible liquids of the parent magma may seperate into two magmatic units.The intermediate rock resulted from seperation of two liquids were incomplete.