Yb3+/Al3+ co-doped silica glasses modified with different amounts of fluorine were prepared by sol-gel method combining with high temperature sintering.The optical and spectroscopic properties of these glasses are investigated in this work.It can be found that both the refractive index and the residual existence of F-content in silica glasses have anomalous variations versus mean F/Si ratio in the starting sol.Refractive index of F/Yb3+/Al3+ triply-doped silica glass can be modified to nearly equal to that of pure silica glass.SiOH concentration of sample glass can be reduced to ~1 ppm by doping moderate content of fluorine.Besides, the maximum refractive index fluctuation △n of the triple doping core glass is about ~4×10-4, and also the fiber core attenuation is 0.2dBm-1 at 1200 nm in this study.Moreover, the glass doped with 9 wt% F/Si in the starting sol has absorption cross section of 2.74 prn2 at 977 nm and lifetime of 890 μs at 1020 nm.This result is in the same order of magnitude with the fluorine free samples.In all, without deteriorating spectroscopic behavior, low SiOH content, high homogeneity, low optical loss and nearly equal refractive index to pure silica glass can be realized in the F-/Yb3+/Al3+ triply-doped silica glass, which is very useful for the design of large mode area fiber.