Based on recent research findings and an analysis of the literature on Precast concrete (PC) small box girders, this paper presents a systematic discussion of the optimization design, materials, and prestressing techniques for PC small box girder structures. The study analyzes and summarizes the optimization design of PC small box girders in terms of diaphragms, prestressing tendons, cross-sectional dimensions, and materials. It synthesizes the impact of these optimization methods on the mechanical performance of PC small box girders. Furthermore, the current research status of retard-bonded and external prestressing technologies is discussed in detail, along with a summary of the mechanical properties of small box girders utilizing these techniques. Finally, several future research directions are proposed on the basis of the current state of research.