Abstract: The macromolecular coupling agent KH570-g-PLA modified sericite were prepared by one-step composite modification process. The effects on the sericite surface modification efficiency of modifier dosage, reaction time and reaction temperature were investigated with the parameters of turbidity, and contact angle of sericite before and after modification, and the optimizational surface modification conditions of sericite were obtained.The optimal technological conditions of KH570-g-PLA modified sericite were that the 10% of PLA was reacted with sericite at 110℃ for 4 h. The turbidity is 809 NTU and the contact Angle is 66°. Compared with unmodified sericite, its turbidity increased by 196%, and contact angle increased by 285%. The coupling agent KH570-G-PLA was successfully coupled to the surface of sericite. And the KH570-g-PLA modified sericite had a smaller crystal size, seldom agglomeration phenomenon, better dispersibility and hydrophobicity, lower crystallinity and the higher heat resistance temperature (about 705℃).