The effect of complementary dual Mach-Zehnder modulators (MZM) structure on photonic time-stretched analog-to-digital converter (PTS-ADC) is studied. The principle that the complementary dual Mach-Zehnder modulators suppress second-order harmonic generation in PTS-ADC is theoretically proved. The PTS-ADC based on dual Mach-Zehnder modulators is designed and simulated in the Optisystem software. The recovery radio-frequency (RF) signal frequency values of PTS-ADC are simulated and compared between dual Mach-Zehnder modulators and single output Mach-Zehnder modulator as electro-optical modulator under the condition of five different input RF signals (10, 15, 20, 25, 30 GHz). The simulation results show that dual Mach-Zehnder modulators can effectively suppress the generation of second-order harmonics and improve the quantization resolution.