A microporous membrane of gamma-Al2O3, with a ceramic plate as substrate was prepared by an in situ graining process. Several important parameters of this gamma-Al2O3 ceramic membrane such as the largest pore radius, the distribution of pore-size, and the most probable pore radius were measured. The effect of basicity of the inorganic poly-aluminum (Al-n(OH)(m)Cl(3n-m)) solution on the morphology and microstructure of the gamma-Al2O3 membrane was investigated with scanning electron microscopy (SEM). Experimental results showed that a high quality gamma-Al2O3 inorganic ceramic membrane could be prepared only when a higher basicity of the poly-aluminum solution was applied.