For the first time to our knowledge, Yb3+/Al3+/P5+/F-co-doped silica preforms were fabricated by sol-gel process combined with high temperature melting technology.We successfully solved the phase separation problem caused by Al/P/F co-doping and the doping homogeneity of the glass rod was very high.The radial variations of the refractive index are around 2.5× 10-4 in a 6 mm diameter and the longitudinal variations of the refractive index are below 2× 10-4 within the length of 50 mm.Furthermore, the refractive index of core glass can be reduced to as low as the value of pure silica glasses with the introduction of F-.The spectroscopic properties of the core glasses are investigated.A photonic crystal fiber (PCF) with a 110 μm Yb3+/Al3+/P5+/F-co-doped core diameter has been fabricated.The slope efficiency is 76%, and the maximum output power is 33 W by the available power.