This paper describes the characteristics of polycrystalline 3C-SiC micro resonators with 3 ×1017 - 1×1019 cm-3 in-situ N-doping concentrations. In this work, the 1.2 μm thick cantilevers and the 0.4 μm thick doubly-clamped beam micro resonators with various lengths were implemented using in-situ doping poly 3C-SiC thin films. The characteristics of the poly 3C-SiC micro resonators were evaluated using quartz actuator and optical read-out vibrometer under vacuum conditions at room temperature. The resonant frequencies of the SiC micro resonators decreased with doping concentrations owing to the reduction of the Young's modulus of the poly 3C-SiC thin films. It was confirmed that the resonant frequencies of the poly 3C-SiC micro- resonators are controllable by adjusting the doping concentrations.