The rhyolitic magma includes two immiscible melts, of which one is more enriched in SiO2 ana depletea in FeO, By contrary, the other is enriched in Fe0 and depleted in Si02. In the view of the melt structure, the former is enricheh in bridging oxygen, and the later--in free oxygen. The depolymeriza- tion of water may lead to changing the melt structure of rhyolitic magma, i, e. lowering its polymerizing degree. Therfore, the viscosity of water-bearing rhy- olitic magma is lawer than that of basalt magma and thus the flow structure is generally well developed in the rhyolite. So that it should avoide mixing the difference between rhyolites and acidic ignimbrite on research work.