A hybrid graphene-TiO2 nanocomposites have been prepared by a facile hydrothermal method to improve the photocatalytic performance and applied for synergetic degradation of fluoroquinolone antibiotic in pulsed discharge plasma (PDP) system. The characterizations of the structure and morphology, chemical bonding state, optical property and electrochemical property show that the graphene-TiO2 nanocomposites can be hybridized successfully. Compared to the pure TiO2, the light absorption range can extend to visible light ( < 505 nm) and the recombination rate of electron-hole pairs declines apparently in the graphene-TiO2 samples. The degradation performance experiment manifests a significant enhancement of the removal efficiency of flumequine (FLU) when the graphene-TiO2 samples are added in the PDP system. The highest removal efficiency can reach 99.4% in PDP/graphene-TiO2 system with 5% graphene content, which is 23.7% and 34.6% higher than that in PDP/TiO2 system and sole PDP system, respectively. Correspondingly, the kinetic constant is 3.5 and 4.6 times higher than that in PDP/TiO2 system and sole PDP system, respectively. The radical species trapping test suggests that (OH)-O-center dot, h(+) and O-2 (-) play the critical role for FLU degradation in PDP/graphene-TiO2 system. The graphene-TiO2 samples can further decompose the O-3 and improve the generation of (OH)-O-center dot and H2O2. The degradation intermediates are determined by LC-MS and IC. The toxicity evolution of FLU reaction solutions is evaluated based on inhibition of photobacterium V. fischeri. Finally, the FLU degradation mechanism in the PDP/graphene-TiO2 system is proposed. This research would provide a novel insight into the application of graphene-based nanocomposites in PDP system as a promising remediation methodology for organic contaminants in water.