A fine $alpha$-Al2O3 powder was prepared by sol-gel process for membrane application. And it was carried out by adding 1.5wt% $alpha$-Al2O3 powders(mean size : 87 nm) as seeds to the prepared sols and by controlling the heating schedule (the heating rate and the soaking time) to prevent the microstructural change, which occured during $ heta$-to $alpha$Al2O3 phase transformation. The seeded $alpha$-Al2O3 particles acted as the heterogeneous nucleation sites for the $alpha$-Al2O3 nucleation during the transformation of $ heta$- to $alpha$-Al2O3 and resulted in increasing the driving force of phase transformation to activate the formation of $alpha$-Al2O3 phase at 82$0^{circ}C$. By $alpha$-Al2O3 seeding and controlling of heating condition the phase transformation of $ heta$- to $alpha$-Al2O3 was accomplished at low temperature and the grain growth process was depressed. Therefore, the unsupported membrane could be fabricated in $alpha$-Al2O3 . The average diameter of pores in the fabricated membrane was 7 nm and the porosity was 47%.