<p>The detrital food web plays an irreplaceable role in carbon and nutrient cycling in forest ecosystems. The function of the diverse microhabitats created by coarse woody debris (CWD) in maintaining the trophic structure of detrital food webs on the forest floor remains poorly understood. To address this gap, we conducted an <i>in situ</i> deadwood decomposition experiment in a subalpine Minjiang fir (<i>Abies faxoniana</i>) forest from August 2013 to May 2021. Invertebrates on the CWD surface and at the soil–CWD interface were collected and identified after 8&#xa0;years of decomposition, and the trophic structure of detrital food webs was analyzed using δ¹³C and δ¹⁵N stable isotope methods. We found that the CWD surface had a greater density and diversity of soil invertebrates compared with the soil–CWD interface. The composition and structure of soil invertebrate communities at the family level were more diverse at the CWD surface than at the soil–CWD interface. Moreover, the stable isotopes of detrital food webs were associated with higher trophic levels and δ¹⁵<i>N</i> values on the CWD surface but higher δ¹³C values at the soil–CWD interface, implying that the CWD-created microhabitats maintain two distinct and interrelated detrital food webs with different trophic structures. We also found that the concentration of organic carbon and the ratio of carbon to nitrogen in food resources were closely correlated with the community composition and trophic structure of detrital food webs. In conclusion, decaying CWD on the forest floor creates heterogeneous microhabitats that promote soil invertebrate diversity and maintain the trophic structure of detrital food webs in forest ecosystems.</p> Graphical Abstract <p></p> <p>Conceptual diagram depicts how coarse woody debris on the forest floor maintains two detrital food webs with different trophic structures.</p>