Li+/Er3+/Yb3+ tridoped CaWO4 polycrystalline powders were prepared by a solid-state reaction method and their upconversion (UC) luminescence properties were investigated in detail. Under 980 nm laser excitation, CaWO4:Li+/Er3+/Yb3+ powder exhibited weak red emission near 680 nm and strong green UC emission peaks at 530 and 550 nm, which were due to the transitions of Er3+ (F-4(9/2), H-2(11/2), S-4(3/2)) -> Er3+ (I-4(15/2)), respectively. The optimum doping concentration of Er3+ was investigated based on crystal structural variation and concentration quenching induced by energy transfer of cross relaxation process in CaWO4. Moreover, the effects of Er3+ concentration on UC emission intensity ratios (S-4(3/2). I-4(15/2) versus H-2(11/2) -> I-4(15/2) and F-4(9/2) -> I-4(15/2)) were studied in detail. (C) 2011 The Electrochemical Society. [DOI: 10.1149/2.036111jes] All rights reserved.