Abstract: Hazelnut (Corylus), as an important non-wood forest trees in China, is renowned for its abundant unsaturated fatty acids and recognized as a "heart-healthy" food. This paper introduces the oil content and fatty acid composition of hazelnuts, analyzes the potential factors that affect these properties. The research progress on phenolic compounds, tocopherols and phytosterols in hazelnut kernels was reviewed. The protein produced as a by-product of hazelnut processing was briefly introduced, and the impact of processing on hazelnut oil was discussed. Literature analysis suggests that the oil content and fatty acid composition in hazelnuts are influenced by variations in growing environments and cultivars. The high content of linoleic acid in hazelnut oil is the primary cause of its susceptibility to oxidative rancidity during processing and storage. Tocopherols and phytosterols have been identified as the main active compounds naturally existed in hazelnut oil, with α-tocopherol and β-sitosterol being the most abundant. These compounds play a crucial role in preventing oil oxidation. Furthermore, phenolics such as gallic acid, syringic acid, vanillic acid and condensed tannin are primarily concentrated in the hazelnut skin, displaying significant variations among different hazelnut varieties. Future research should explore the application of emerging technologies and the synergistic application of active antioxidant ingredients in hazelnut oil.