With the incorporation of noble metal materials, photonic crystal fibers (PCFs) could be performed as an effective platform for refractive index sensing of the filling analytes. Furthermore, by coating functional dielectric layers upon the metal surfaces, the resonance energy transfer is modulated from the core mode of the PCFs towards the surface plasmon resonance mode of the metals, and the sensing performance could be boosted. Here, considering that the exciton-plasmon coupling is efficient between perovskite quantum dots (QDs) and gold, a kind of CsPbBr3 QDs/Au bilayer coated triangular-lattice PCFs has been simulated numerically as the refractive index sensors. With the optimization of the QDs and gold layer thicknesses, together with the variation of the central hole size of the PCFs, in the refractive index (RI) region of 1.26 to 1.34, a rather narrow full width at half maximum (FWHM) of the loss spectra was achieved as 13.74 nm when the central hole size was 1.28 μm and the highest figure of merit was 63.79 RIU (the central hole size was 1.53 μm). This work demonstrates that the analyte identification accuracy was enhanced by FWHM narrowing of the loss spectra; in addition, taking the abundance of the material choice of perovskite QDs into consideration, more analytes could be detected effectively. Moreover, by adopting asymmetric structures, the sensitivity of the PCFs based refractive index sensors could be further improved.