Abstract: The latest research progresses of micro-nano robots (size ranges from 1 nm~1 mm) in the years of 2017~2021 are reviewed. Firstly, the advances of micro-nano robots in micro-nano manipulation, swarm control and targeted therapy are reviewed from four perspectives: physical propulsion, chemical propulsion, biological propulsion and hybrid propulsion. Then the potential challenges to the applications of micro-nano robots are discussed from preparation, localization and imaging, functionalization, and swarm. Finally, the research progresses of micro-nano robots are summarized and the development trends are prospected.