Microbial dark carbon fixation (DCF) is a key biogeochemical process in which chemoautotrophic or heterotrophic microbes convert inorganic carbon to organic carbon in the absence of light. Recent studies have shown that the contribution of this process to the global carbon cycle has long been underestimated, particularly in deep waters, sediments, soils, hot springs, and other extreme environments where it holds significant ecological importance. This review comprehensively summarizes the recent research advances in microbial DCF, with a focus on major carbon fixation pathways, functional microbial groups, and carbon fixation rates across different ecosystems. The published data demonstrate significant variations in microbial DCF rates across different ecosystems. The deep ocean exhibits the highest DCF rate, reaching approximately 2.14×10⁴ µmol C/(m²·d), followed by boreal lakes, where the maximum DCF rate reaches 1.33×10⁴ µmol C/(m²·d). Additionally, in the deep-water layer of stratified boreal lakes, the contribution of DCF to total primary productivity can be as high as 81.4%. In high-temperature hot spring environments, DCF can account for 80%-100% of the total carbon fixation. From the perspective of carbon fixation pathways, the Calvin cycle is the primary pathway for microbial DCF across various habitats, widely existing in ecosystems including lakes, oceans, soils, and hot springs. Meanwhile, different habitats adapt to their specific environmental conditions by incorporating additional metabolic pathways such as the Wood-Ljungdahl pathway and the reductive tricarboxylic acid cycle (rTCA) pathway to achieve efficient carbon fixation. Temperature, pH, salinity, oxygen concentration, nutrient conditions, and depth are key environmental factors regulating microbial DCF rates. These factors collectively determine the efficiency and contribution ratios of DCF processes in different ecosystems by influencing the community structure of DCF-related microorganisms, the selection of metabolic pathways, and enzyme activities. Finally, the review discusses current limitations in this field, including uncertainties in quantification methods and insufficient understanding of environmental response mechanisms, and highlights key directions for future research. These advances are expected to provide critical scientific evidence for improving the carbon cycle theory, assessing the impacts of climate change, and developing microbe-based carbon sequestration technologies.