An integrated, tunable spectrometer based on a silicon-on-sapphire platform is designed at wavelengths of 2.29–2.35 μm. Its pivotal component is a 4.7 μm-radius ring resonator on a graphene monolayer. Its full width at half-maximum and free spectral range are ～1.5 and ～45 nm, respectively, as found through a numerical simulation and theoretical computation. Sixteen characteristic peaks are obtained by tuning the Fermi level of graphene. The gap between the ring and waveguides is increased by 0.5 μm to increase the resolution, and though this can drastically reduce the transmission rate, an upper sapphire layer maintains light to the drop port.