Reported here is femtosecond laser mediated bandgap tailoring of graphene oxides (GOs) for direct fabrication of graphene-based microdevices. When femtosecond laser pulses were used to reduce and pattern GO, oxygen contents in the reduced region could be modulated by varying the laser power. In this way, the bandgap of reduced GO was precisely modulated from 2.4 to 0.9 eV by tuning the femtosecond laser power from 0 to 23 mW. Through the first-principle study, the essence of GO bandgap tailoring is proved to be femtosecond laser reduction induced oxygen-content modulation. As representative illustrations, bottom-gate graphene FETs were fabricated in situ by using femtosecond laser reduced GO as the channel material, and an optimized room temperature on off ratio of 56 is obtained. The controlled reduction of GO by femtosecond laser contributes great potential for bandgap tailoring and microdevices patterning of graphene future electronics. toward