Voltage　sag　has　become　the　most　serious　power　quality　problem.　Since　voltage　sag　is　inevitable,　risk　assessment　becomes　the　key　link　to　reduce　its　impact.　Firstly,　three　kinds　of　risk　quantitative　indicators　for　voltage　sag　are　analyzed,　and　the　risk　assessment　methods　are　divided　into　three　categories:　simulation-based,　state　estimation-based　and　data-driven　risk　assessment　methods.　The　advantages,　disadvantages　and　applicable　scenarios　of　each　method　are　summarized.　Secondly,　the　paper　points　out　the　technical　challenges　faced　by　voltage　sag　risk　assessment　in　the　context　of　new　power　system.　Finally,　the　future　research　direction　of　voltage　sag　risk　assessment　is　prospected,　in　order　to　provide　reference　for　related　research.　©　2023,　State　Power　Economic　Research　Institute.　All　rights　reserved.