Nicotinamide phosphoribosyltransferase (NAMPT) is a crucial metabolic enzyme that plays a pivotal role in the nicotinamide adenine dinucleotide (NAD) synthesis pathway. Nicotinamide adenine dinucleotide (NAD+), an important intracellular coenzyme I, has important functions in a multitude of biological processes, including energy metabolism, DNA repair, and cell signaling. NAMPT stimulates the synthesis of NAD+ by catalyzing the reaction between nicotinamide (NAM) and 5-phosphoribosyl-1-pyrophosphate (PRPP). A number of studies have demonstrated a close relationship between the activity of NAMPT and the level of intracellular NAD+. This has been shown to have an important influence on the maintenance of intracellular energy homeostasis and biological clock rhythms and redox balance. In addition, the expression level of NAMPT is regulated by a variety of internal and external factors, including nutritional status, oxidative stress, and inflammation. Therefore, NAMPT is not just a key enzyme in the NAD synthesis pathway but also an essential regulator of intracellular energy metabolism and biological clock regulation. A comprehensive investigation of the functional mechanism of NAMPT may facilitate the elucidation of its potential roles in the pathogenesis of disease and serve as a theoretical foundation for the development of novel therapeutics.