Based on 0.18 μm CMOS process, a low-variable tuning gain LC-VCO(inductance capacitance-voltage controlled oscillator) was designed for wireless communication and radar systems. The circuit includes a distributed bias varactor array and a switched capacitor array, a reasonable selection of the bias voltage can achieve the purpose of expanding the C-V(capacitance-voltage) curve, thereby effectively reducing the tuning gain within the entire tuning voltage range. The three-bit switched capacitor array divides the entire adjustable frequency range into 8 sub-bands, which is implemented by controlling the varactor array. And the switched varactor array is adopted, which can effectively suppress the variation of the LC-VCO tuning gain. Based on the model of 1P6M 0.18 μm technology, the post-layout simulation results show the good performance on property of tuning gain variation rate, which is 21.5% with the frequency tuning range from 9.13 GHz to 11.15 GHz, at the same time, the VCO DC power consumption is 9 mW with 1.8 V supply voltage, the phase noise is -105 dBc/Hz@1 MHz when the VCO oscillating frequency is around 10 GHz.