Abstract: In recent decades, coastal ecosystems have been severely degraded due to overfishing, pollution, and habitat destruction. Marine ranching, as an important ecological restoration strategy, aims to enhance biodiversity and rebuild ecosystem functions. However, its effects on meiobenthic communities and their trophic dynamics remain insufficiently understood. Here, we combined biomass size spectra (BSS) and stable isotope analysis to investigate how marine ranching reshapes BSS and trophic niches of meiofauna in the Bohai Sea. Results showed that the mean biomass of meiofauna in the marine ranching area (138.8±66.3) μg dwt./10 cm² was markedly higher than that in the control area (39.1±14.8) μg dwt./10 cm²; P<0.01), while the overall shapes of the BSS were similar between the two areas. Sediment organic carbon (SOC) was significantly positively correlated with the biomass of several size classes, whereas ammonium nitrogen was negatively correlated with the biomass of several size classes (P<0.05). Compared with the control area, meiofauna in the marine ranching area exhibited significantly lower δ¹³C and δ¹⁵N values (P<0.05), suggesting potential changes in the composition/degree of reworking of the available organic matter pool and in the community-level effective trophic position. In addition, the isotopic niche width of meiofauna was significantly larger in the marine ranching area (SEA=0.343‰²) than that in the control area (0.265‰²), indicating a broader resource-use breadth and more diverse potential food sources. Overall, marine ranching may enhance meiobenthic biomass and promote resource-use diversification by improving benthic habitat conditions and reshaping basal energy pathways. This study provides scientific support for evaluating ecological effects and guiding the management and sustainable development of marine ranching.