The effects of Al2O3, Yb2O3, Er2O3 and OH- on spectral properties of P2O5.Na2O.SrO.Al2O3.Yb2O3.Er2O3 erbium phosphate glass were studied. 5, 8, and 13 mol% Al2O3, 4, 5, 6, 7 and 8 mol% Yb2O3 and 0.05, 0.2, and 0:4 mol% Er2O3 were used. It was found that Al2O3 can improve fluorescent lifetime of Er3+ ions, but the integrated absorption cross section of Er3+ ions decreases with the increase of Al2O3 concentration. Evaluating from energy transfer efficiency of Yb3+ to Er3+ and spectral parameters of Yb3+ and Er3+, we conclude that 6 mol% Yb2O3 and 0:4 mol% Er2O3 are needed for LD pumped microchip laser applications. OH- groups in glass affect greatly fluorescent intensity and lifetime of Er3+, Yb3+:phosphate glass. The OH- absorption coefficient at 3000 cm^(-1) should be less than 1 cm^(-1) for laser applications. Pumped with a 2-W, 974-nm InGaAs laser diode, CW laser centered at 1530 nm with slope efficiency of 10:6 % and maximum output of 43 mW was achieved in our 2-mm-thick Er3+, Yb3+:phosphate glass at room temperature.