Abstract: To reveal the synergetic effect of microwave radiation on the macroscopic mechanical properties and microscopic pore structure of shale, and to explore the possibility of enhancing rock breaking and improving shale gas recovery by regulating the microwave temperature to influence the pore structure. Taking the Longmaxi Formation shale from the Changning-Weiyuan Block in Sichuan as the test sample, the uniaxial compression test system was used to evaluate the degree of macroscopic mechanical property deterioration of the shale. In the low-temperature N₂ and CO₂ gas adsorption experiments, the potential impact of the cyclic adsorption and desorption process on the pore test results was considered, and the experimental data were corrected to obtain more accurate pore structure parameters. The fractal FHH model was applied to quantify pore structure evolution under microwave radiation, with detailed analysis of pore complexity changes across different microwave treatment stages.Results show that microwave radiation alters shale adsorption behavior: CO₂ adsorption increases in the low-pressure region, while total N₂ adsorption initially rises and then declines. Microwave treatment dynamically affects pore structure: at early stages, specific surface area and micropore volume temporarily decrease due to the closure and contraction of ultra-micropores (<0.5 nm), while macropore volume increases; At mid-stages, overall micropore volume increases significantly; at later stages, micropore volume decreases compared to the initial state, and the proportion of mesopores increases. Pore complexity is highest in pores >5 nm, followed by pores in the 2–5 nm range, and lowest in micropores, which exhibit highly concentrated size distributions. As microwave temperature increases, pores below 5 nm show reduced size uniformity and increased complexity/irregularity, while pores above 5 nm exhibit reduced spatial complexity and surface roughness. Micropore development is the key factor controlling specific surface area and average pore size. Microwave radiation significantly weakens mechanical properties; with increasing temperature, the failure mode transitions from brittle to plastic. Macro-fracturing and micro-damage exhibit multi-scale synergistic effects: macro-instability is driven by increased macropore volume, while micro-damage evolution requires higher cumulative temperatures to reach equilibrium. Pore structure evolution is the underlying cause of mechanical property degradation.