A modified sol-gel method combined with high-temperature sintering has been developed to make large size Yb3+-doped silica glass rod (Φ3 ~ 18 mm) with high optical quality and low background loss.The optical and spectroscopic as well as laser properties of Al-Yb, Al-P-Yb, Al-F-Yb and Al-P-F-Yb doped silica glasses and fibers prepared by this method have been systematically researched [1-4].Table 1 shows the main spectroscopic properties and impurity contents of Yb3+-doped silica glass.Fig 1 shows the outstanding properties of Yb3+-doped silica core-glass and fibers.Compared with traditional MCVD method, the better optical homogeneity and larger core size can be realized with this sol-gel method.Through the treatment with reactive gas, background loss of fiber can be controlled to be 0.05 dB/m.A photonic crystal fiber (PCF) with 100 μm Al-Yb co-doped core diameter has been fabricated.A maximum average amplified power of 310 W and peak power of 1.5 MW have been realized in the pulse amplification test.In addition, 83.3% laser slope efficiency is achieved in the continuous laser mode from this PCF.To the best of our knowledge, this is the highest slope efficiency from Yb3+-doped silica PCF prepared by non-MCVD method.