Graphene quantum dots (GQDs), a smart functional nano-sensing material, present excellent thermo-optic properties. Here a novel fiber-optic temperature sensor based on GQDs solution encapsulated in hollow core fiber (HCF) is first proposed. GQDs with the small size less than 20 nm are successfully filled in the inner part of HCF by capillarity, and the compact sensing probe is length of 6 mm. The relationships of the photoluminescence (PL) peak, intensity, and full-width at half-maximum of the PL spectra are investigated with temperature changing from 10 °C to 80 °C. The photoluminescence peak wavelength and the self-referenced intensity all present good sensitivities, which are 123.7 pm/°C and - 0.01375/°C, respectively.