In this paper,a new automatic amplitude control (AAC) scheme for the design of low-noise,low power LC-VCO is presented. Instead of using a traditional current source,a digitally-tuned resistor array is introduced to improve phase noise performance of LC-VCO.The proposed LC-VCO is designed in 0.18ɥm RF CMOS process,and the tuning range is from 1.4GHz to 2.3GHz under a control voltage from 0.1V to 1.7V. The typical phase noise is -127.23dBc/Hz at 1MHz offset from a 1.85GHz carrier while consuming 496ɥA current from a 1.8V supply.The FoM and FoMT of the proposed VCO are -193.06dBc/Hz and -206.7dBc/Hz respectively.