Abstract: Carbohydrates play a crucial role in the development of chronic diseases, and although research in this area is expanding, the precise definition of carbohydrate quality remains unclear. Currently, commonly utilized indicators encompass dietary fiber content, whole grain intake, free sugars intake and the glycemic index (GI). High-quality carbohydrate foods typically exhibit high dietary fiber content, consist of whole grain components, contain low levels of free sugars, and possess a low GI. The GI, in particular, directly influences the human blood sugar response and serves as a vital measure for describing carbohydrate quality. This article provides a comprehensive overview of the factors that influence the GI, focusing on three aspects: digestion and absorption, processing methods, and starch composition and structure. It further examines the GI values of various food sources. The rate of digestion and absorption, as well as diverse processing methods, can influence the GI. Additionally, the composition and structure of starch directly affect the GI. Amylose and amylopectin exhibit dissimilar structural compositions, with amylopectin containing more amylase binding sites than amylose, leading to a higher digestion rate. Consequently, foods with elevated amylose content tend to have relatively low GI values. Additionally, starch can be categorized into three types (A-type, B-type, and C-type) based on the crystal form of amylopectin present in the starch. Among these types, A-type starch is the most readily digestible, while B-type and C-type starch exhibit low GI characteristics due to their reduced digestibility. By studying the microstructure of starch, researchers can gain valuable insights into the influencing factors of the GI, thereby introducing a fresh perspective to the assessment of food carbohydrate quality.