FLASH radiotherapy is a novel method that has the potential to improve the therapeutic gain ratio to a new level. FLASH radiotherapy technology is mainly characterized by irradiation at ultra-high dose rate, which can reduce radiation-induced injury to normal tissues during radiotherapy, while maintaining the ability of radiation damage to tumors. On the one hand, as a new radiotherapy technology, the radiobiological mechanisms of FLASH are unclear, which hinders its clinical transformation. On the other hand, there are many technical difficulties in the clinical application of ultra-high dose rate irradiation technology. This paper summarizes the research progress of radiobiological mechanisms underlying FLASH radiotherapy, as well as the challenges and possible solutions associated with FLASH radiotherapy treatment plans, to provide a reference for clinical translation of subsequent FLASH radiotherapy.