Abstract: The promotion of a carbon-neutral power system necessitates the development of efficient, innovative, intelligent, and low-carbon technologies. One crucial aspect in achieving this goal is the upgrading of the low-rank coal industry. The rotary kiln technology emerges as a highly promising solution for low-rank coal pyrolysis, owing to its remarkable adaptability to various raw materials, flexibility, and scalability. To shed light on the current state and future prospects of low-rank coal pyrolysis in rotary kilns, we first summarize the characteristics of existing technologies. And the main factors that influence the yield and quality of products during the pyrolysis process are identified. This paper further delves into the theoretical aspects by providing insights into material transport, crushing mechanisms, and heat transfer mechanisms within the rotary kiln. Additionally, the various techniques employed for upgrading low-rank coal in rotary kilns are analyzed. Then, main bottlenecks and challenges that hinder the development of low-rank coal pyrolysis in rotary kilns are concluded. Based on these analyses and summaries, we propose a forward-looking perspective on the research focus areas and development directions for low-rank coal pyrolysis. Our aim is to provide technological guidance for the large-scale development of low-rank coal pyrolysis technology.