In this paper, a 60-GHz ultra-low-power single-ended sub-harmonic down-conversion mixer with a merged structure fabricated in 90-nm CMOS is presented. The mixer core is merged directly with self-biased trans-impedance amplifier (TIA) to omit its traditional load stage and to enhance the conversion gain. By using weak-inversion bias technique in a source-driven topology, the mixer core only needs quiescent μA which can be stolen from TIA via the feedback resistors. The sub-harmonic mixers can work effectively for millimeter wave system by employing LO frequency that is only half of fundamental mixer. When operating with the optimal LO power of -3.5 dBm at 30 GHz, power consumption is 1mW. The measurement results of the mixer show 5.9 dB conversion gain, -60 dBm 2LO-to-RF leakage at 60 GHz. The calculated figure of merits (FOM) with the consideration of conversion gain and power consumption is the best among the reported mixers operating at V-band frequency in CMOS process.