Different　concentrations　of　TiO2　co-doped　NaYF4:　15%　Yb3+,　2　%　Er3+　powder　phosphors　were　synthesized　by　the　high　temperature　solid　state　reaction　process.　The　samples　were　investigated　by　X-ray　diffraction,　scanning　electron　microscopy　and　photoluminescence　testing.　The　results　show　that,　under　the　980　nm　excitation,　the　NaYF4:　15　%　Yb3+,　2　%　Er3+,　x　%　TiO2　(x　=　0,　1,　5,　7,　10)　composite　shows　several　emission　peaks　at　521,　540,　and　655　nm.　With　the　increase　of　doping　TiO2　that　the　luminescence　intensities　of　both　Yb3+　and　Er3+　emission　increase　firstly,　and　reach　a　maximum　at　1　mol%　TiO2,　and　then　get　suppressed　with　the　further　increase　of　TiO2　doping.　Our　results　suggest　that,　for　Yb3+-Er3+　co-doped　NaYF4　with　doping　TiO2,　there　will　be　a　high　potential　in　application　of　novel　light　conversion　devices,　especially　in　solar　cells.