Recently,the temperature-dependent up-conversion luminescence of materials doped with lanthanide ions has been drawing spectacular attention on account of their potential applications in thermal imaging,cancer treatment,temperature sensors,optical refrigeration as well as the optical heater.Especially,lots of efforts have been focused on non-contact temperature sensors based on the fluorescence intensity ratio(FIR)of the up-conversion materials.With no contact with the tested object,FIR-based technique can be applied in some special environment,such as building fire detections,electrical transformer temperature in power stations,corrosive circumstances and biological systems.Being independent of spectrum losses and excitation source fluctuation,FIR technique possess high reliability,improved sensitivity and widened operating temperature range compared to some other optical-based techniques,such as fluorescence lifetime and amplified spontaneous emissions.