煤炭地下气化(UCG)产业化有助于煤炭能源结构转型发展，提高煤炭资源的低碳化利用水平，是一项符合可持续发展战略的环境友好型能源开发技术。20世纪80—90年代的国际能源危机，促使美国大力发展UCG技术，先后开展了6大系列UCG先导试验，极大推进了UCG技术进步，为全球现代UCG技术的形成提供了关键基础。系统收集整理美国40余年的UCG先导试验成果，梳理关键技术发展路径，目的是为我国正在推进的UCG技术产业化进程提供启示和借鉴。研究表明，美国通过UCG先导试验和技术探索，确定了适宜于UCG技术的煤层和煤质条件，创新发展了钻井式UCG方法和工艺，尤其是发明了可控后退式注入点(CRIP)和双水平井(P-CRIP)技术，提供了气化通道建造、气化过程控制、合成气质量提高三方面技术难题的解决方案；提出了相邻孔腔相互融合的技术思路，为从单炉开始扩大UCG气化规模奠定了可行基础。在政府层面上组织实施系统的协同科技研发计划，是美国UCG技术创新能力持续释放的关键。同时，美国UCG系列试验尚有诸多技术难题有待进一步解决，如UCG炉地质密封性及其动态监测评价、气化通道动态监控与稳定性、煤层充分气化保障技术、炉宽安全有效扩展技术、UCG炉环境监测与控制、与碳减排密切结合的UCG技术等，为我国UCG技术发展提供了需要关注的重点方向。

The industrialization of underground coal gasification (UCG), which is conducive to the transformation and development of the coal energy structure and the improvement in the low-carbon utilization level of coal resources, is an environmentally friendly energy development technology in line with the sustainable development strategy. The international energy crisis from the 1980s to the 1990s prompted the United States to vigorously develop UCG technologies. Accordingly, this country has successively carried out six series of UCG pilot tests, which contribute greatly to the progress in UCG technologies and provided the critical foundation for the formation of modern UCG technologies worldwide. This study systematically collects and summarizes over 40 years of UCG pilot test results in the United States and sorts the development paths of key technologies, with the purpose of providing inspiration and a reference for the ongoing industrialization process of UCG technologies in China. The results show that the United States has determined the coal seams and coal quality suitable for the applications of UCG technologies through UCG pilot tests and technical exploration. Moreover, this country has innovatively developed drilling-type UCG and relevant processes. Most especially, it has invented the controlled retractable injection point (CRIP) and parallel CRIP (P-CRIP) technologies, providing solutions to three technical challenges: gasification channel construction, gasification process control, and synthesis gas quality improvement. The United States has proposed the technical philosophy of the mutual fusion of adjacent cavities, which lays the feasible foundation for expanding the scale of UCG gasification from a single gasifier. The systematic collaborative R&D (research and development) schemes of science and technologies organized and implemented at the governmental level are the key to the longstanding innovation of UCG technologies in the United States. Nevertheless, there are still many technical challenges to be further solved in the UCG test series in the United States, such as the geological sealing performance of UCG gasifiers and its dynamic monitoring and evaluation, the dynamic monitoring and stability of gasification channels, technologies for guaranteeing the full gasification of coal seams, technologies for the safe and effective expansion of the gasifier width, the environmental monitoring and control of UCG gasifiers, and UCG technologies closely combined with carbon emission reduction. These challenges provide the focus for the development of UCG technologies in China.