Tm3+, Yb3+ co-doped CaWO4 polycrystals are synthesized via the high temperature solid state method. Under excitation of a 980 nm laser, the up-conversion fluorescences based on the transitions 1G4→3H6, 1G4→3H4, 3H2→3H6 and 3H3→3H6 in the visible light region are successfully obtained. The effect of the concentration change of Yb3+ on the luminous intensity of Tm3+ is discussed. Meanwhile, the temperature properties of the red up-conversion fluorescences centered at 689 nm and 705 nm are studied in a tem-perature range between 313 and 773 K according to the fluorescence intensity ratio method. It is found that the temperature can be monitored by detecting the red up-converion fluorescences of Tm3+, Yb3+ co-doped CaWO4 polycrystals. The maximal sensitivity of temperature measurement can be achieved to be 5.7×10-4 K-1 at 458 K.