According　to　many　studies,　motor　vehicle　collisions　lead　to　many　deaths　and　disabilities,　and　bring　about　huge　economic　losses　to　societies　and　individuals　around　the　world.　If　risky　scenarios　could　be　recognized　and　the　driver　could　be　timely　warned,　the　frequency　of　traffic　accidents　could　be　reduced　effectively,　and　traffic　safety　could　be　improved.　This　article　summarizes　the　current　state　of　the　research　on　safety　warnings　under　connected　vehicle　environments-from　risk　recognition　algorithms,　collision　avoidance　systems,　dangerous　event　identification　and　notification　methods,　real-time　safety　warning　system　and　effects　of　various　types　of　warning　information　notifications.　At　the　end　of　this　article,　the　conclusions　of　this　work　are　presented,　and　possible　future　directions　for　safety　warning　research　under　connected　vehicle　environments　are　discussed.　This　article　represents　the　current　research　status　of　safety　warnings　under　connected　vehicle　environments　to　some　extent,　which　can　provide　references　for　future　safety　warning　research　in　terms　of　framework,　methods　and　technologies,　etc.