Abstract: Nonionic polysaccharides, a class of natural macromolecules characterized by hydroxyl groups serving as both anchoring groups and the primary hydrophilic groups, act as selective depressants for a diverse range of minerals. This includes non−polar minerals (such as talc, molybdenite, and graphite) as well as polar oxides, sulfides, and salt−type minerals. Their adsorption mechanisms on mineral surfaces differ fundamentally from those of conventional ionic reagents. This study systematically summarizes the selective depression regularities of nonionic polysaccharides as flotation reagents, revealing that variations in their molecular structures do not affect the ranking of their depression strength across minerals. Further analysis demonstrates that the depression strength ranking of nonionic polysaccharides exhibits a strong correlation with the polar characteristics (hydrophilic/hydrophobic nature) and acid−base properties of mineral surfaces. Building upon this correlation, a comprehensive review of recent advances in the mechanisms and criteria governing their selective depression performance provides further validation for the hypothesis that adsorption onto polar minerals is predominantly mediated by acid−base interactions. The synthesis further identifies that current research primarily focuses on validating the applicability of diverse nonionic polysaccharides as flotation depressants, expanding their utility to broader mineral systems, and developing surface modification approaches to enhance selective depression performance. Nevertheless, comparative evaluations of separation efficacy across polysaccharide types remain inadequate, while techno−economic viability in practical ore processing requires thorough investigation. These critical knowledge gaps should constitute a central focus for future research on polysaccharide−based depressants.