Abstract: Solar flares, a major form of solar eruptive activities, release strong electromagnetic radiation that can disrupt the Earth’s Thermosphere-Ionosphere-Magnetosphere (M-I-T) coupling system. In the past decade, significant progress has been made. This review systematically overviews the multi-scale effects of solar flares on the M-I-T system and their coupling mechanisms. For the thermospheric response, we highlight flare-induced heating, changes in neutral composition, and atmospheric dynamical processes; for the ionospheric disturbances, we review the sudden photoionization response, variations in electron density, and the restructuring of electric fields and current systems via electrodynamic processes. Special attention is given to the delayed effects of the flare extreme ultraviolet late phases on the ionosphere. In magnetospheric coupling, we discuss the modulation of field-aligned currents and magnetospheric convection structures through changes in polar conductivity. We also explore the nonlinear coupling characteristics under the combined influence of solar flares and geomagnetic storms. We highlight the significant contribution made by Chinese researchers to the understanding of flare energy transmission and distribution mechanisms within the M-I-T system.