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Up-conversion phosphors BaLa 2 ZnO 5 co-doped with Ho 3+ /Yb 3+ were synthesized by high temperature solid-state reaction method. The phase composition of the phosphors was characterized by X-ray diffraction (XRD). The structure of BaLa 2 ZnO 5 : 0.75% Ho/15% Yb phosphor was refined by the Rietveld method and results showed the decreased unit cell parameters and cell volume after doping Ho 3+ and Yb 3+ , indicating Ho 3+ and Yb 3+ have successfully replaced La 3+ . Under the excitation of 980 nm diode laser, the strong green and weak red up-conversion emissions centered at 548 nm, 664 nm and 758 nm were observed, which originating from 5 S 2 , 5 F 2 → 5 I 8 , 5 F 4 → 5 I 8 and 5 S 2 , 5 F 2 → 5 I 7 transitions of Ho 3+ ions, respectively. The optimum doping concentrations of Ho 3+ and Yb 3+ were determined to be 0.75% and 15%, and the corresponding Commission International de L'Eclairage (CIE) coordinates are calculated to be x =0.298 and y =0.692. The related UC mechanism of Ho 3+ /Yb 3+ co-doped BaLa 2 ZnO 5 depending on pump power was studied in detail. The results indicate that BaLa 2 ZnO 5 : Ho 3+ /Yb 3+ can be an effective candidate for up-conversion yellowish-green light emitter. [ABSTRACT FROM AUTHOR]