<p>The 1550&#xa0;nm InGaAsP/InP electro-absorption modulator (EAM) is one of the key components for the data communication applications. To enhance the comprehensive performance of EAM, the continuous iterative optimization is required in both the theoretical mechanisms and the fabrication processes. This paper analyzed the physical mechanisms of EAM by calculating the normalized overlap integral between the electron and the hole energy levels, which yielded the red shift and the absorption intensity of the absorption band under the reverse bias. By analyzing the absorption spectra of the wavelength and the reverse bias, the transmission loss and the extinction ratio at different wavelengths were determined. By optimizing the key parameters such as the barrier composition, the barrier width, the quantum well width, and the number of quantum wells, the extinction ratio of the EAM was improved. The introduction of the P-doped InGaAsP layer into the P-doped waveguide mitigated the electric-field peak at the interface between the P-doped cladding and the P-doped waveguide, thereby further enhancing the modulation efficiency. This study systematically simulated and analyzed the key parameters of the design for the 1550&#xa0;nm InGaAsP/InP EAM, providing the theoretical reference value for achieving the high-performance EAM.</p>