The structural characteristics and the key influencing factors of self-assembled nanogratings within GeO2 glass are investigated by using an ultrafast laser system with tunable repetition rate and pulse duration. The formation threshold of nanogratings in GeO2 glass is experimentally determined, which is dependent on material bandgap and laser pulse duration. In addition, based on the optimization of process parameters and the use of birefringence of nanogratings, the micro-optical components are fabricated within GeO2 glass and their functions are demonstrated. Moreover, the influence of repetition rate of femtosecond laser on the formation and structural properties of nanogratings is also analyzed. It is found that the birefringence strength of nanograting in GeO2 glass has an anomalous polarization dependence, and the corresponding origin is speculated.