Cuscutae Semen is a Chinese herbal medicine and a raw material for health foods in China, with flavonoids being a group of its main functional components. This article provides a systematic review of the extraction and purification techniques-reflux, ultrasonic, Soxhlet, microwave-assisted, flash, enzymatic hydrolysis, and supercritical CO₂ extraction methods-of flavonoids from Cuscutae Semen. Furthermore, it elaborates on the biological activities such as reproductive protection, anti-tumor effect, anti-oxidative stress effect, liver and kidney protection, and immune regulation of flavonoids from Cuscutae Semen, as well as their related mechanisms. Moreover, this paper makes an outlook on the development prospects of flavonoids in Cuscutae Semen in terms of green intelligent extraction, mechanism analysis, and applications.