This paper presents a comprehensive theory of a dual-frequency complex load-matching technique based on transmission lines. The theoretical analysis is insightfully described, and the applicable regions of the design equations are specified. To substantiate the theory, a corresponding methodology is proposed to design a dual-band 10/24-GHz amplifier, which is fabricated by standard 0.13-μm 1P8M CMOS technology. This amplifier involves synthetic quasi-TEM transmission lines to build the dual-frequency matching circuits. The comparisons between simulations and on-wafer measurements are reported to establish the feasibility and flexibility of the presented technique in microwave applications.