Yb/P/Al codoped silica glass preforms are fabricated by MCVD process combined with the solution doping technique. Highly and homogeneously doping of Yb3+ is realized by optimization of the core composition and fabrication process. The Yb2O3 concentration in preform core is up to ~4 wt.% and Yb3+ fluorescence lifetime at 1080nm reaches 1 780 μs. Doubleclad fibers with octagonal inner cladding are successfully drawn from the preform, the fiber core diameter is 7.5 μm and the clad absorption coefficicent is up to ~5 dB/m@976 nm. The operation of the cladding pumped allfiber laser is demonstrated using Ybdoped doubleclad fibers. Fiber lasers with output power of 5.15 W and slope efficiency of 76% are obtained.