Abstract: In recent years, China has introduced the N78 and N79 frequency bands in 5G Sub-6 GHz applications, making 5G dual band antennas that can cover these two frequency bands quickly become a current research hotspot. However, there are few papers proposed that can balance small size and N78 and N79 dual band broadband coverage. Based on this background, this paper proposes a design with small plane size for terminal applications. A new method of low-profile quarter mode substrate integrated waveguide (QMSIW) dual frequency antenna. This antenna is based on the substrate integrated waveguide (SIW) technology. First, a quarter mode substrate integrated waveguide antenna with the advantage of miniaturization is constructed. Its first two modes (TE₁₀₁ mode and TE₃₀₁ mode) are used to form two bands, and then parasitic patches are introduced through magnetic coupling. The first two modes of parasitic patches (TE₁₀₁ mode and TE₃₀₁ mode) are used to expand the bandwidth of the two bands. The simulation results show that the three-dimensional size of this antenna is 21 mm×25 mm×1.6 mm (0.25λ₀×0.3λ₀×0.019λ₀) (λ₀ is the wavelength in the air at the center frequency) the dual band coverage of N78 (3.4−3.6 GHz) and N79 (4.8−5 GHz) is ultimately achieved. The physical test results show that this antenna can obtain −6 dB impedance bandwidth located in the N78 frequency band 5.8% (3.35−3.55 GHz) and N79 frequency band 5% (4.69−4.93 GHz), respectively. The average efficiency in the low and high frequency bands is −1.6 dB and −1.8 dB, respectively.