Abstract: Squalene is a biologically active and naturally occurring substance with an all-trans isoprene structure, and it is widely used in food, medicine, cosmetics and other fields. A growing market for squalene requires in-depth research, including the development and utilization of squalene resources, ensuring the quantity and quality of squalene sources, and making the functional properties of squalene reasonable and more highly utilized. This paper reviews the source, extraction and functional properties of squalene, compares the advantages and disadvantages of animal, microorganism and plant source, as well as the main extraction and purification methods, and discusses the research progress on the functional properties of squalene. It has been found that the content of squalene in vegetable oils and their processing by-products, Chinese medicinal materials, tea, and other plants have high levels and are currently safe and efficient sources of squalene. In particular, the content of squalene in old tea leaves of tea is comparable to or even greater than that in olive and amaranth oils. The mainstream extraction and purification methods of squalene are summarized and compared, and it is found that the new extraction and purification methods, such as liquid-liquid extraction, supercritical fluid extraction, and solid-phase extraction, have clear advantages in terms of extraction time, separation effect and environmental protection. Other extraction methods such as magnetic nanoparticles, microwave, ultrasonic assisted, and silver ion complexation can be used as complementary to these. It is worth mentioning that the current extraction methods of squalene are difficult to apply in industry. However, processing models can be used to reduce difficulties in industrial separation and purification. In addition, this review discusses the nutritional function and role of squalene in regulatory mechanisms, further illustrates its potential applications in regulating the immune system, promoting cardiovascular health, and inhibiting cancer and bacteria, which will provide new ideas for optimizing the separation and purification of squalene.