Phthalate was synthesized via the esterification by phthalic anhydride with aliphatic alcohols when sodium hydrogen sulfate was used as the catalyst. The effects of the length of aliphatic alcohols, types of aliphatic alcohols and content of branched-chain aliphatic alcohol on the properties of phthalate were studied systematically, which can offer the effective theoretical foundation for synthesis of high performance lubricants. Results showed that viscosity and viscosity index of phthalates increased, but their pour point and flash point reduced with an increaseof the length of aliphatic alcohols. For phthalate prepared from aliphatic monohydric alcohol with same carbon atom number, these branched-chain esters had higher viscosity, pour point, flash point, and lower viscosity index than these straight-chain esters. The synthetic esters formed by reacting phthalic anhydride with a mixture of linear and branched aliphatic monohydric alcohol showed properties: high viscosity, low viscosity index, good high-temperature behavior and worse low-temperature behavior. The increase of the branched-chain aliphatic alcohol led to higher viscosity, lower viscosity index. And the pour point and flash point showed serrated variation along with it.