A novel technology of in-situ coating Al2O3 on the surface of H4TiO4 was developed to prevent the aggregation of nano-TiO2 powders and improve the dispersibility and thermal stability in the way of forming a uniform coating layer. The heterogeneous nucleation was conducted to prepare the precursor of nano-TiO2 and then Al2O3was coated on the surface of precursor. The effects of Al2O3 in-situ coating on the properties of nano-TiO2 were investigated. The results show that H4TiO4 can be dispersed well under alkaline condition (pH 8.5) and the heterogeneous nucleation can be controlled easily. The optimized uniform coating layer is obtained by adding 5% (mass fraction ) and 10% of Al2O3 and the aggregation of nano-TiO2 powders is effectively inhibited and the dispersibility is obviously improved. The crystal sizes of TiO2 powders are 12.3, 11.4 and 8.7 nm after coating 0, 5% and 10% of Al2 Os respectively. Al2O3 on the surface of particulates in amorphous phase could increase the thermal stability of nano-particles after calcined at 550 C.