As a representative subtropical plateau wetland ecosystem in China, Caohai Lake is characterized by abundant aquatic flora and fauna resources and high ecological value. However, recent intensification of eutrophication has triggered massive decline of submerged macrophytes, driving the gradual regime shift from a macrophyte-dominated clear-water state to an algae-dominated turbid-water state, profoundly impacting ecosystem functions and biodiversity. Based on field investigations conducted during 2022-2023, this study systematically examined the current status and characteristics of macroinvertebrate communities in Caohai Lake, comparing differences with historical data from macrophyte-dominated periods (1983 and 2014), thereby revealing the response mechanisms of macroinvertebrate communities during the regime shift. Results showed that current macroinvertebrate communities exhibited a mean density of 146.49 ± 16.62 ind./m2 and biomass of 15.93 ± 14.02 g/m2, with Shannon-Weiner diversity index (0.73 ± 0.06), Margalef richness index (0.37 ± 0.03), and Pielou evenness index (0.66 ± 0.04). Functional feeding groups comprised 94.69% collectors, 2.81% predators, 1.58% scrapers, and 0.92% filter-feeders. Spatial distribution patterns of macroinvertebrate communities corresponded with submerged macrophyte distribution. Biomass showed significant seasonal variation (p < 0.05), being higher in autumn and winter than spring and summer, while other community characteristics exhibited no significant seasonal differences. Redundancy analysis identified dissolved oxygen (DO), water depth (WD), pH, permanganate index (CODMn), transparency (SD), and conductivity (Cond) as key environmental drivers. Over two decades, CODMn showed persistent increase while Chl.a concentration rose and SD declined annually post-regime shift. Comparative analysis revealed dominance of scrapers (Gastropoda) during the clear-water state versus gather-collectors (Tubificidae and Chironomidae) in the turbid-water state, with higher species richness, density, biomass, and diversity indices observed during the macrophyte-dominated phase. This study provides critical scientific basis for comprehensive assessment of Caohai Lake"s aquatic ecosystem status, understanding macroinvertebrate responses during plateau lake regime shifts, and implementing targeted ecological restoration measures.