Poly(2-methoxy-5-octoxy)-p-phenylene　vinylene　(PMOCOPV)/titanium　dioxide　(TiO2)　nanocomposites　with　different　contents　of　TiO2　nanoparticles　were　prepared　by　in-stiu　polymerization　and　their　microcosmic　structure　and　properties　were　characterized　by　scanning　electron　microscope　(SEM),　tunneling　electron　microscope　(TEM),　X-ray　diffraction　(XRD)　and　thermogravimetry　(TG).　The　results　show　that　TiO2　nanoparticles　are　not　blended　with　PMOCOPV　simply　but　encapsulate　by　PMOCOPV.　The　nanocomposites　are　spheric　particles　that　disperse　uniformly　and　the　diameter　of　nanocomposites　is　around　at　60　nm~80　nm.　The　crystallinity　of　nanocomposites　is　improved　with　the　increase　of　content　of　TiO2　nanoparticles　and　the　thermal　stability　of　nanocomposites　is　also　enhanced　in　contrast　to　PMOCOPV.