The effects of two silane coupling agents (KH550, KH570) and three coupling agents of organic titanate (JSC, CT136 and NTC401) on the surface modification of superfine Al2O3 powders were tested and compared. The results showed that three coupling agents of organic titanate succeeded in modify the surface of Al2O3 particle from hydrophilic property to lipophilicity, while two silane coupling agents failed. The group changes of the surface were confirmed by IR spectrum, which also indicated that chemical absorption occurred between NTC401 and the powders surface, but for JSC and CT136 mainly occurred physical absorption. SEM photos of the powders showed that agglomeration-free particles could be obtained when the powders were treaded by NTC401. However, when treated by JSC or CT136 the powders tended to be secondly agglomerated. The proper coupling mechanism was analyzed, and it was thought that space structure of octahedral complex of titanium ion with six ligands could effectively impede agglomeration.