The　photonics　sensor　with　heterojunctions　of　TiO2/PS/p-Si　was　prepared　by　coating　the　nano-sized　thin　film　of　TiO2　on　surface　of　the　porous　silicon　substrate　and　was　characterized　by　the　surface　photovoltage　spectroscopy.　The　results　showed　that　the　photovoltage　of　porous　silicon　(PS/p-Si)　was　greatly　increased　two　to　three　orders　of　magnitude　by　coating　TiO2　thin　film.　The　enhancement　of　photovoltage　may　be　attributed　to　the　efficient　absorption　spectrum　from　near　infrared　till　ultraviolet　light　of　the　double　heterojunctions　of　TiO2/PS/p-Si　and　the　effective　separation　of　the　photoproduced　electron-hole　pairs　due　to　the　increment　of　the　built-in　electric　field　of　the　quasi-intrinsic　porous　silicon.　Moreover,　the　back　electric　field　generated　by　the　potential　difference　between　PS　and　p-Si　may　resist　the　diffusion　of　minority　carrier　toward　the　electrode,　leading　to　the　effective　enhancement　of　photovoltage.