A multiloop method is presented for highly nonlinear ring oscillators in this paper. This circuit permits lower tuning gain through the use of coarse/fine frequency control, which also translates into a lower sensitivity to the voltage at the control lines. A 8-GHz VCO in SMIC 0.18μm 1P6M CMOS technology is designed. The linear tuning range of VCO is from 7.95 to 8.45GHz with the tuning voltage vary from 0 to 1.8V. The post simulation result shows that the power consumption is 48mW, the phase noise of the proposed VCO is -88.24dBc/Hz at 1MHz and -113.2dBc/Hz at 10MHz, and core chip area is 130μm × 120μm.