Long-afterglow phosphor is a unique photoluminescent energy-saving material having widespread applications in the areas of displays, biomedicine, energy, and environmental engineering. Sr₂MgSi₂O₇∶Eu²⁺,Dy³⁺, as representative silicate material, is one of the most promising long-afterglow phosphors owing to its excellent water resistance, good chemical stability, and long afterglow time. However, its further commerical application is limited by insufficient afterglow intensity, narrow emission bands, and unclear afterglow mechanism. In this review, we give a comprehensive introduction of the history of Sr₂MgSi₂O₇∶Eu²⁺,Dy³⁺ long-afterglow phosphor. In addition, we summarize the recent advances of Sr₂MgSi₂O₇∶Eu²⁺,Dy³⁺ in terms of afterglow mechanism and diverse applications, including safety signs, bio-imaging, and photocatalysts. Finally, the urgent problems to be solved and potential future directions of Sr₂MgSi₂O₇∶Eu²⁺,Dy³⁺ are discussed.