Abstract: With the rapid improvement on the communication technology of RF transceiver,high performance voltage-controlled oscillator has been the key link of analog integrated circuit design,production and implementation.Focus on the problem of phase noise,a design for a 1.115GHz LC VCO is proposed in TSMC0.18μm CMOS process.The circuit is simulated by the SpectreRF in Cadence.The simulation results presented that the VCO voltage adjustment range is 4Vto 6V,and output frequency range is 1.114 69GHz to 1.115 38GHz.Phase noise at an offset of 10kHz,100kHz and 1MHz are-90.9dBc/Hz,-118.6dBc/Hz and-141.3dBc/Hz,respectively.In order to enhance the VCO noise performance,the paper's purpose is as much as possible to exchange narrow frequency for good phase noise.