Abstract: Soil colloids serve as the core interface for nutrient retention and transformation in soil, and their structural stability directly impacts soil fertility and the cycling efficiency of key elements such as carbon and phosphorus. As an essential approach for enhancing fertilizer utilization efficiency, fertilizer synergists inevitably interact with soil colloid system in regulating nutrient transformation processes, thereby exerting profound effects on soil structure and function. This review summarizes the functional characteristics of major fertilizer synergists, including composite inhibitors, biostimulants, organic types (containing organic synergists, organic acid), humectant surfactants, and liquid/sodium-containing salt preparations. It also delves into the complex processes in which synergists indirectly regulate soil organic carbon sequestration and phosphorus availability through altering colloid-aggregate environments and microbial activity. The paper highlights that the ultimate environmental effects of synergists are highly scenario-dependent, with their benefits and drawbacks balanced by the degree of alignment between synergist type, application method, and initial soil properties. This paper provides a theoretical foundation for scientifically assessing the ecological risks of fertilizer synergists and their application in precision agriculture.