Abstract: Microalgal CO₂ fixation has emerged as a promising approach for climate change mitigation and sustainable energy development, offering dual benefits of greenhouse gas reduction and low-carbon economic advancement. Nevertheless, the widespread implementation of this technology is currently constrained by suboptimal CO₂ fixation efficiency. This investigation systematically evaluates the impact of six amine absorbents: monoethanolamine （MEA）, diethanolamine （DEA）, triethanolamine （TEA）, 2-amino-2-methyl-1-propanol （AMP）, 2-（2-aminoethylamino）ethanol （AEEA）, and diethylenetriamine （DETA）—on CO₂ fixation efficiency and biomass production in Nannochloropsis oceanica. Under simulated flue gas conditions （15% CO₂+85% N₂）, the supplementation of 50 mg/L AMP demonstrated superior performance, achieving peak biomass mass concentration （1.07 g/L） and CO₂ fixation rate （292.8 mg/（L·d））, representing significant enhancements of 21.7% and 44.5% compared to the blank group, respectively. Furthermore, AMP, TEA and DEA were found to substantially promote lipid accumulation, with lipid contents reaching 45.94%, 44.88%, and 44.48% of dry cell weight （DCW） respectively, compared to 41.51% DCW in the control group. Superoxide dismutase （SOD） activity assays revealed that amine solvents induced mild oxidative stress but caused no significant cellular damage, with AMP exhibiting the lowest cytotoxicity （SOD activity: 6.1 U/mg）. Transcriptomic analysis further uncovered the molecular mechanisms underlying AMP-mediated carbon metabolism regulation. AMP treatment markedly upregulated key enzymes such as phosphoglycerate kinase （PGK） and dihydrodiol dehydrogenase （DHDH）, synergistically enhancing CO₂ fixation and lipid biosynthesis pathways. KEGG enrichment analysis identified significant involvement of glycolysis/gluconeogenesis, unsaturated fatty acid biosynthesis, and photosynthetic carbon fixation, providing a theoretical foundation for the growth-promoting effects of AMP. Additionally, the upregulation of nitrogen metabolism-related genes （e.g., nitrate transporter NRT and nitrate reductase NR） optimized carbon-nitrogen metabolic balance, supporting rapid microalgal growth. This study not only validates the efficacy of amine solvents in microalgal CO₂ fixation but also delineates their molecular regulatory networks through multi-omics approaches, offering novel insights for developing high-efficiency, low-toxicity CO₂ bioconversion technologies.