Ultrafast modulation of electron-phonon couplings via laser excitation has been experimentally demonstrated, yet a clear microscopic understanding remains elusive. Here we establish the first framework combining time-dependent density functional theory, density functional perturbation theory, and Migdal-Eliashberg theory to track electron-phonon couplings and superconductivity in prototypical phonon-mediated superconductor MgB${}_2$ under laser illumination. We find that near-infrared laser pulses induce charge transfer from boron $\sigma$ to $\pi$ orbitals, effectively renormalizing the electron-phonon couplings and boosting the superconducting critical temperature to $$52 K. The simulated thermalized superconducting gaps match well with experimental measurements. We propose a generalizable route for ultrafast modulation of superconductivity in materials whose dominant electron-phonon coupling channel can be selectively addressed by light, with photoinduced changes in electronic coupling and screening playing a central role. This work offers fundamental insight into non-equilibrium optical control of electron-phonon interactions and superconductivity, and provides a predictive tool for studying photo-modulated electron-phonon coupling and macroscopically observable superconducting properties.