Collagen, as a thermal-sensitive protein, is the most abundant structural protein in animals. Native collagen has been widely applied in various fields due to its specific physicochemical and biological properties. The beneficial properties would disappear with the collapse of the unique triple helical structure during heating. Understanding thermal stability of collagen is of great significance for practical applications. Previous studies have shown the thermal stability would be affected by the different sources, extraction methods, solvent systems in vitro and modified methods. Accordingly, the factors affecting thermal stability of collagen are discussed in detail in this review.