Abstract: The phase asymmetry of the mixers’ intermodulation (IM) products is studied in this paper based on the second-order memory mechanisms. This study is developed based on the time-varying modulation function (TVMF) and multi-box behavioral mixer (MBBM) model. This phase asymmetry manifests in the phase where the lower and upper third intermodulation (IM3) products have inverse changing trends vs. tone spacing. The research shows that the inverse trends of the phase of the upper and lower IM3 products are caused by baseband modulation and second harmonics modulations. However, the upper and lower IM3 products’ phase inverse trend mechanism created by baseband modulation is different from that created by second harmonics modulations, and thus may be readily distinguished. Finally, the phases of the upper and lower IM3 products of the mixer are simulated based on advanced design system (ADS), and the above analysis is verified with the measured results.