Graphene due to its unique properties of biocompatibility has received considerable attention for biosensing applications. Here, we report the effect of glucose oxidase treatment on the graphene devices. Raman spectroscopy and the electrical transport measurements are performed to study the graphene intrinsic characteristics before glucose oxidase treatment. The absence of the defect peak in the Raman spectrum shows high-quality graphene. The modulation in the electrical properties is further investigated by different period of glucose oxidase treatment. Our results illustrate that the mobility of the graphene-based field effect transistor is gradually enhanced with the glucose oxidase treatment time. The enhancement in the electrical performance of graphene FET with the biomolecules could be the suitable route for the bioelectronic devices.