Large-size (φ =5mm) and good homogeneity (refractive index fluctuation An <2× 10-4) yb3+-doped Al2O3-SiO2 and Al2O3-P2O5-SiO2 core glasses were prepared by sol-gel method.Their optical properties were evaluated.It was found out that the addition of Al3+ or ps+ ions had a great influence on the redox state of ytterbium ions.With increasing Al3+ ions content in these silica glasses, more trivalent Yb3+ ions were reduced to divalent Yb2+.On the contrary, the increase of ps+ ions content greatly promoted divalent Yb2+ ions to be oxidized into trivalent Yb3+.The possible redox mechanisms have been explored and discussed in detail.Both large mode area double cladding fiber (LMA DCF) with core diameter of 48 μm and large mode area photonic crystal fiber (LMA PCF) with core diameter of 90 μm were prepared from these core glasses.81 W laser power with a slope efficiency of 70.8% was achieved from yb3+-doped A12O3-SiO2 LMA PCF.And the few-mode fiber with good beam quality (M2 =1.4) was achieved from yb3+-doped Al2O3-P2O5-SiO2 LMA PCE The transmission loss at 1200 nm is 0.4 dB/m.