Ba₂GdF₇ was prepared by hydrothermal method and water bath method respectively:Yb³⁺、Er³⁺and Ag²Snanomaterials were prepared by positive and negative electric attraction method to obtain Ba₂GdF₇@SiO₂@Ag₂S nanomaterials.The Ba₂GdF₇@SiO₂@Ag₂S nanomaterials were characterized by XRD and FT IR.The light source selection and luminous intensity stability of the nano material were studied.Temperature sensing and photothermal conversion properties of the composite nanomaterial were investigated by excitation of 980 nm and 808 nm laser.The results showed that the temperature measurement sensitivity S_a(absolute sensitivity) and S_r(relative sensitivity) of Ba2GdF7@SiO2@Ag2S nanomaterials reached the maximum values at 343 and 303 K，with the maximum values of 0.005 8 K^-1 and 1.059 8%·K^-1，respectively.The photothermal conversion efficiency of the composite nanomaterials reached 628%.The results are compared with those in the same field，and it is found that its temperature measurement and photothermal conversion ability are at a higher level in the research in the same field.