Plant secondary invasion reduces the efficiency of invasive plants controlling and hinders the restoration of invaded ecosystems. Studies on plant secondary invasion are still rare in China, so it is urgent to strengthen international communications and learn from foreign experience. The English term secondary invasion is highly inconsistent, which brings obstacles for scientific communication. In this review, different definitions of secondary invasion were sorted out and discriminated, and the mechanisms of secondary invasion were summarized. Four common definitions of secondary invasion mainly include secondary expansion, secondary diffusion, inducing invasion, and secondary invasion. Provenance effect, control side-effect, legacy effect, and global climate change are the mechanisms underlying secondary invasion. In the future, more comprehensive control strategies are needed, that is, it should simultaneously suppress the possible secondary invasive plants and strive to alleviate the legacy effects of the targetplants, and add local plants to improve system resilience and inhibit secondary invasion.