Abstract: Based on deformed AZ80 magnesium alloy as the substrate, micro-arc oxidation (MAO) and micro-arc composite (MC) coating were prepared on its surface. Slow strain rate test (SSRT), combined with microscopic morphology observation, was employed to investigate the stress corrosion cracking (SCC) susceptibility and SCC mechanism of the deformed magnesium alloy and its protective coatings in a stress-electrochemical coupled environment. The results show that both MAO and MC coatings exhibited good resistance to stress corrosion cracking, with the MC coating demonstrating the lowest stress corrosion susceptibility. During the preparation process, the MAO coating developed micropores and oxide particles, which tent to induce stress concentration. In contrast, the MC coating effectively filled the microporous structure of the MAO coating, thereby enhancing its corrosion resistance. The MC coating could effectively prevent stress corrosion cracking of the deformed AZ80 magnesium alloy.