Water erosion of rare earth tailings poses significant ecological risks, while moss crusts are widely distributed across these tailings. However, their role in erosion mitigation remains poorly understood. Using a single-raindrop simulation experiment, this study quantified the kinetic energy reduction capacity of moss crusts at four developmental stages (I: bare soil; II-IV: increasing cover, biomass, and height). Key results include: (1) Moss crusts markedly increased the accumulated kinetic energy required to disrupt the surface (Emoss). At 1 cm thickness, Emoss values for developmental stages II, III, and IV were 0.04, 0.18, and 4.61 J, respectively--stage IV exhibited 363-fold greater resistance than bare soil (stage I). (2) After moss removal, the underlying soil's resistance (Eunder) dropped sharply (averaging 0.01 J across stages), with no differences between developmental stages. Moss crusts reduced raindrop kinetic energy by 65.04% (stage II), 92.79% (stage III), and 99.72% (stage IV). (3) Resistance correlated strongly with slope and soil moisture: air-dried crusts exhibited higher Emoss (0.35 J) than wet samples, and steeper slopes (25 degrees-30 degrees) increased Emoss by 10-fold compared to flat terrain. These findings demonstrate that moss crusts act as effective physical barriers against splash erosion, offering a scalable strategy for ecological restoration of degraded rare earth tailings in subtropical regions.