To investigate the change trends of plasma D-dimer during catheter-directed thrombolysis (CDT) in acute lower limb ischemia (ALI) patients and their clinical value. A retrospective review of patients with ALI who received CDT was carried out. The repeated measurements of plasma D-dimer were analyzed by generalized estimating equations (GEEs) and the change trends of D-dimer were analyzed by spline regression approach. A total of 150 patients were included. Among them, 3 days of CDT was ineffective in 41 cases, effective in 33 cases and markedly effective in 76 cases. The results of GEEs analysis showed that serum D-dimer changed significantly with time (time effect, P < 0.001). Serum D-dimer levels of patients with different treatment outcomes were different after treatment (group effect, P < 0.001), and serum D-dimer levels in these three groups showed different trends over time (group*time effect, P < 0.001). The different trends in serum D-dimer level with time after treatment in the three groups could be directly seen in the spline regression curve (P < 0.001). The plasma D-dimer changes regularly during CDT for ALI. We can predict the efficacy of CDT and guide adjustments of the therapeutic regimen according to the trend of D-dimer changes during thrombolysis.