Abstract: The ytterbium doped silica fiber is widely used in high power laser facility. However, few reports had been done on the structure relaxation behaviors with temperature in the ytterbium doped silica glass. In this work, we prepared the Yb3+ doped Al2O3-P2O5-SiO2 bulk glass with sol-gel method combining with high temperature sintering. The annealing was done at different temperature on the glass. The density, fictive temperature, refractive index and spectroscopic properties of the annealed Yb3+ doped Al2O3-P2O5-SiO2 glasses have been characterized. The structures of these glasses were tested by NMR and EPR. The physical and optical property change mechanism is explained by local structure change of Yb3+ and coordination number change of Al3+ and P5+ ions in the Yb3+ doped Al2O3-P2O5-SiO2 glass.