Continuous renal replacement therapy (CRRT) is effective in treating acute kidney injury (AKI), but it requires anticoagulants. The study was conducted to compare the anticoagulant effect of low-molecular-weight heparin (LMWH) sodium and sodium citrate on AKI patients treated by CRRT. The medical records of 150 severe AKI patients treated by CRRT in the Second Affiliated Hospital of Hainan Medical College (China, Hainan) from January 2020 to January 2023 were analyzed retrospectively. LMWH sodium was administered as an anticoagulant for 72 patients in the control group, and the remaining 78 receiving sodium citrate were enrolled into the observation group. Outcomes compared between groups included coagulation indices, inflammatory factors and renal function indices prior and post therapy, filter lifespan and adverse reactions. Post therapy, in contrast to the control group, the observation group showed notably lower prothrombin time (PT) and activated partial thromboplastin time (APTT) levels and a notably higher platelet (PLT) level (P < .05) and presented notably lower C-reactive protein (CRP) and interleukin-6 (IL-6) levels (P < .05). In contrast to the control group, the observation group experienced a notably longer filter service life and a notably lower total incidence of adverse reactions (P < .05). Sodium citrate had a better anticoagulant effect than LMWH for severe AKI patients treated by CRRT, improving renal function and filter longevity with fewer adverse effects.