This comprehensive review summarized literatures of electron-FLASH, in vitro and in vivo studies of proton- and carbon-FLASH therapy, and the first human study of proton-FLASH. The possible mechanisms of FLASH effect was discussed including hypoxia, DNA repair and response and immune modulation. This review pointed out the current major issues of developing FLASH with particle therapy including the lack of stringent verification of dosimetry and solid reporting on beam characteristics, doses administered and quality control.