The influences of hydroxylation on grafting of aminopropyltrimethoxysilane ((CH3O)(3)-Si-CH2-CH2 CH2-NH2, abbreviated as APS) and fabrication of CaSO4/PVC composite were investigated in this paper. The experimental results indicated that the pre-treatment of CaSO4 particles by NaOH promoted the formation of OH-, which enhanced the grafting of APS on CaSO4 surface and improved the interfacial adhesion between CaSO4 and PVC matrix. Compared with the use of CaSO4 with sole APS modification, the use of the CaSO4 with NaOH and APS modification led to the increase of the impact strength of the CaSO4/PVC composite from 36.5 kJ m(-2) to 50.2 kJ M-2 and the flexural strength from 48.7 MPa to 62.1 MPa. (C) 2015 Elsevier B.V. All rights reserved.