Abstract: In order to reveal the effect of γ-methacryloxypropyl trimethoxysilane (MPS) on the structure and property of SiO₂-polyacrylate (PAcr) composite particles, MPS, MPS modified SiO₂ (MPS-SiO₂) nanoparticles, and the raw dispersions obtained from the modification of SiO₂ nanoparticles with MPS were used as the additives in the radical suspension copolymerization of butyl acrylate and methyl methacrylate. The influence of the amount of coupled and uncoupled MPS and the ratio of coupled MPS to uncoupled MPS on the crosslinking degree and crosslinking structure of SiO₂-PAcr composite particles was investigated, and the shear orientation abilities of the composite particles with different crosslinking structures were compared. TEM observation shows that some irregular particles with diameter at about 6 nm are formed by the hydrolytic condensation of uncoupled MPS (i.e. MPS condensed particles). The MPS condensed particles can act as the crosslinking points owing to the double bonds on their surface. By adding the raw dispersions from MPS modification of SiO₂ nanoparticles, dual-crosslinking structure can be formed in the SiO₂-PAcr composite particles because both coupled and uncoupled MPS are included in the polymerization system. The as-prepared dual-crosslinked particles can be deformed into the orientated structure with a high aspect ratio of 12.0 in HAAKE torque rheometer. However, the aspect ratio after the same shear orientation process can only reach 8.8 and 9.1 with coupled or uncoupled MPS as additives, respectively. The coupled and uncoupled MPS can lead to two different kinds of crosslinking structures, which improves the shear orientation ability of SiO₂-PAcr composite particles synergistically.