Abstract: Given the heterogeneity of fruit quality and the increasing consumer demand for high-quality fruit, consumers are more inclined to focus on the quality of fruit rather than its price. Traditional methods for classifying fruit quality mainly rely on manual visual inspection or simple mechanical sorting. This approach not only has low efficiency but also causes mechanical damage to fruits and results in higher operation costs. Consequently, spectral technology, recognized for its ease of operation, high accuracy, and non-destructive nature, has been widely adopted for non-destructive fruit inspection to meet consumer needs. Research has shown that near infrared spectroscopy (NIR) possesses non-destructive, convenient, and efficient characteristics, and, when combined with chemometric methods, has played an important role in analyzing fruit composition, determining the ripeness, and detecting mildew. This paper reviews the theoretical foundations and development history of NIR non-destructive detection technology, and outlines the analytical processes and technical implementation paths of this technology, and provides examples of NIR spectroscopy's application in measuring the sugar content in fruits..