This paper studies the phase morphologies of glass-forming Zr65Cu17.5Ni10Al7.5 alloy during unidirectional solidification, as well as the gravity influence on them. The direction of the microstructure became worse when the moving speed of the furnace exceeded a critical value. This critical speed was about 5mm/min for Zr65Cu17.5Ni10Al7.5 alloy in the present experiments. Different relationship between the direction of the movement of the solid-liquid interface and the gravity field led to different states of buoyancy convection, and finally different phase morphologies were obtained. When the movement direction was the same as the gravity vector, the primary phase was less and finer without an evident transition region in front of the interface. However, when the two directions were opposite to each other, more and coarser primary phase was obtained with an evident transition region appearing in front of the interface.