Abstract: Firstly, the application requirements of lower extremity exoskeletons in rehabilitation, industry as well as military fields are introduced briefly, and the pros and cons, research problems and applicable population of rigid and soft lower extremity exoskeletons (RLEEX/SLEEX) are analyzed and compared. Subsequently, the research process and progress of SLEEX at home and abroad are illustrated in great detail, especially in mechanisms and actuation, sensors layout, development of control strategies as well as assessment of the assistance performance. Finally, the key technologies related to the SLEEX, including soft structure, human intention recognition, control strategies and assistance assessment, are summarized, and the future research direction is prospected.