Abstract: Modern protected livestock with excellent production capacity, environmental friendliness and economic revenue is an inevitable requirement to promote the modernization of agriculture. This study took protected pigs as the research object, used emergy method to evaluate the social, economic and ecological levels of China's protected livestock production systems in 2021 at the provincial scale. The emergy input structure and emergy flow of the production system were first determined to reveal its internal composition and correlation. Then, indicators such as labor service level, emergy-money profit and emergy sustainability index were proposed to evaluate the regional heterogeneity of protected pig production systems in China. Based on the long-term development requirements of agricultural production system, the emergy index for sustainable development of the system was revised, and the optimization path of sustainable protected livestock production with regional differences was discussed. The results showed that: (1) The protected pig production system mainly depended on non-renewable purchased emergy, and the feed supply accounted for the largest proportion (68.60%). (2) The labor service level and emergy-money profit of protected production were better than those of backyard, but some provinces still had a net loss of money. The labor service level of the protected production in the provinces with negative or low profit were generally low, which were mostly concentrated in the northwest and northeast of China. (3) The environmental loading ratio in the southern region were generally higher than those in the northern region. The emergy sustainability index of Shaanxi, Ningxia, Jilin and Heilongjiang were significantly better than the national level, but had lower emergy-money profit. The emergy index for sustainable development of Guizhou and Guangxi were best. (4) Compared with 2021, The emergy index for sustainable development of the stereoscopic multilayer pig production system expected to be completed in 2030 had increased by 23.33%. In the future, we should further improve the protected breeding rate of pig production in China, economic policies should be adopted to address the deficit of provinces with negative returns, and the measures of precision feeding, stereoscopic breeding and green planting-breeding circular will be effective optimization paths to improve the sustainability of protected livestock production systems. This study provides a better understanding of the sustainable management of protected livestock production systems.