Hexagonal NaYF4:Yb3+,Er3+ (β-NaYF4:Yb3+,Er3+) nanoparticles supported on TiO2 nanobelts were prepared using two-step procedures of ion-exchangeable process and hydrothermal treatment:layered titanate nanobelts were first ion-exchanged with Y3+ Yb3+ and Er3+ cations to produce titanate nanobelts with these cations,and then,the product nanobelts in NaY solution were treated under hydrothermal condition to transform into anatase TiO2 nanobelts supported with β-NaYF4:Yb3+,Er3+ nanoparticles.The final products were characterized by various measurement techniques.Many preparation conditions,e.g.,the content of added precursors,reaction time and pH value,were optimized to obtain nanocomposites including relatively uniform nanoparticles with strong upconversion (UC) emission intensity.The measurement results showed that the anatase TiO2 nanobelts,supported by the large number of β-NaYF4:Yb3+,Er3+ nanoparticles with 30-70 diameter range and very strong UC emission,could be achieved under suitable preparation condition.The UC emission intensity of the nanoparticles with the concentrations of Yb3+ and Er3+ closer to 20 mol.% and 1 mol.% was the strongest.