Human milk oligosaccharides (HMOs) are important nutritional components in breast milk, and sialyllactose (SL) is one of the core members of HMOs. HMOs play an important role in regulating the gut microbiota of infants, especially in the reproduction and metabolic regulation of the dominant gut microbiota in early life-Bifidobacterium. The sources of SL are diverse and there are various methods available to prepare it, providing multiple alternative pathways for its industrial application. However, the interaction mechanism between SL and Bifidobacterium is complex, and there are still many difficulties that need to be overcome, which affects the combined application of SL and Bifidobacterium in the food and other industries. Therefore, this review covers three aspects: the formation pathways of SL, the carbohydrate uptake behavior and HMOs metabolism of Bifidobacterium, and the mechanism of SL on Bifidobacterium, focusing on the latest advances in related fields. The aim is to provide scientific reference for promoting the application of SL and Bifidobacterium in the development of breast milk substitutes and functional foods.