Abstract: Given (CH₃SH) critical role as an industrial intermediate and environmental pollutant, investigating variations in its physical property under applied electric fields holds significant scientific and practical value. In this study, we systematically calculate a series of physicochemical properties of CH₃SH under varying electric field intensities using density functional theory (DFT) with the B3LYP functional and 6-311+G(d,p) basis set. Key parameters examined include: total energy, critical bond lengths, dipole moment, infrared (IR), Raman, and ultraviolet-visible (UV-Vis) spectra, as well as tunneling effects. Furthermore, potential energy curves derived from scans enables comprehensive analysis of methyl mercaptan's dissociation behavior under applied electric fields. Results demonstrate that electric fields profoundly modulate CH₃SH's molecular geometry, electronic properties (reflected in dipole moments and spectral shifts), and dissociation pathways by altering potential energy barriers.