Silica nanotube, SNT, was used to prepare composite sheets of polymethyl methacrylate, PMMA, which showed improved flexural modulus than the virgin PMMA sheet. Surface of silica nanotube was treated by methacryloxypropyl trymethoxysilane, MPMA, to give better particle dispersion in the composite during melt mixing with PMMA through the twin screw extruder. Weight of MPMA in treated SNT was measured to be 7.5 percent of SNT by a thermogravimetric analyzer. The flexural modulus of SNT/PMMA composite was measured to be increased up to by 15% as the SNT content in the composite increased by 5%. Light transmittance decreased with SNT content in the composite, however, SNT with MPMA treatment showed better light transmittance than that without MPMA. 5% of MPMA treated SNT composite showed 80% of light transmittance, however, 5% of untreated SNT composite showed only 30%. TEM showed that the particle dispersion of MPMA treated SNT in the composite was better than without MPMA treatment. Breaking strength and strain decreased simultaneously with increasing SNT in the composite, but it did not look to be related to the treatment of MPMA on SNT.