Green-glazed porcelain sherds excavated from the Southern Song and Yuan strata of Laohudong kiln site at the foot of Fenghuangshan Hill in Hangzhou were adopted as test samples. Based on the physico-chemical principles for crystallization and phase separation of the glazes, microstructure and phase composition were investigated by means of energy-dispersive X-ray fluorescence, X-ray diffraction, high temperature microscopy, field emission electron microscopy and transmission electron microscopy. For the first time, the study demonstrates that the glazes from both the Southern Song and Yuan strata are crystalline-phase separated glazes. The influences of microstructure and composition upon color generation and formation of jade-like feel are discussed.