Abstract: Walnut (Juglans regia L.) belongs to the genus Juglans of the family Juglandaceae, with a long history of cultivation and a great production in China. It is rich in carbohydrates, fats, proteins, minerals and vitamins, which exhibits high nutritional value and unique medicinal effects. Walnut oil, extracted from walnut kernels, is rich in unsaturated fatty acids and contains a variety of characteristic components such as phytosterols, tocopherols, squalene and phospholipids. These characteristic components endow walnut oil with diverse biological activities. The main characteristic components of walnut oil are summarized in this article. It also reviews walnut oil’s antioxidant, cardiovascular disease prevention, memory function improvement, anti-inflammatory, protection of intestinal health, antitumor, and other biological activities. Additionally, it summarizes the existing problems in the current research on walnut oil and prospects future research directions. The objective is to provide scientific basis for further research and comprehensive development and utilization of walnut oil.