This article proposes low-power class-C voltage-controlled oscillator (VCO) with double-balanced mixer. The oscillator consists of a dual-resonance LC resonator in shunt with one pair of capacitive cross-coupled nMOSFETs. The common source of cross-coupled nMOSFETs is connected to the ground through a tail transistor in shunt with a capacitor, dynamic bias is applied to the gate of the tail. The proposed oscillator has been implemented with the tsmc 0.18μm CMOS technology and the core current and DC consumption of the oscillator are 2.535 mA and 2.99 mW, respectively at the dc drain-source bias of 1.18V. The oscillator can generate differential high-band and low-band signals at 4.286GHz and 2.94GHz respectively. The die area of the class C oscillator is 1.187×1.109 mm2. The layout dimension of the mixer is 0.6×0.7 mm2.