Abstract: Based on Gilbert unit,this paper uses a 0.18μm CMOS process to design a high gain,low noise down -conversion double balanced mixer which works in 5.25GHz.In order to reduce the current through the switch transistor and load,and to remit the limit of voltage margin and consumption,a current injection technology is used in this mixer;A resonant inductance is used to restrain the charging and discharging of the parasitic capacitance to reduce the current which inflows the parasitic capacitance,so as to reduce flicker noise;an inductance inserted on the source of transconductance to is form a negative feedback circuit and to improve the circuit's linearity.Base on 0.18 mm CMOS process and 1.8V supply voltage,the post simulation results show that,the mixer has a good output characteristics in 250 M Hz intermediate frequency and a good circuit matching,the test gets a conversion gain of 22. 65dB,IIP3 of 7.66dBm,and SSB noise is 5.58dB in intermediate frequency 250M Hz.The power consumption of the circuit is 8.64mW.