A 5.8GHz low voltage, high linear and isolation transformer based mixer using 0.18μm CMOS process for WLAN receiver was investigated. The proposed fully integrated transformer featured that biasing, coupling, and filtering functions in an RF input stage commutated the input RF voltage to current, which was coupled to local oscillator (LO) switching pairs. This implementation excluded the current source transistor at bottom and furthermore reduced the supply voltage. The designed mixer required only a 0.8V supply voltage and consumed less than 10mW DC power. A high third-order intercept point of +3dBm and an input second-order intercept point of +19dBm had been achieved. The excellent LO/RF and RF/IF isolations were achieved up to 54dB and 74dB, respectively.