Objective To explore the effect of poly-L-lactic acid in the treatment of lower eyelid depression after external blepharoplasty. Methods From November 2022 to March 2023,21 patients with lower eyelid depression after external blepharoplasty admitted to our hospital were selected as the research objects. Poly-L-lactic acid was used for injection treatment of lower eyelid depression. The skin improvement before and after treatment was observed, and the total effective rate was calculated. Results The patients were satisfied with the recovery of depression after three injections. The total effective rate was 95.23% (20/21) after 1 month of follow-up, and the average skin gloss improvement was 2 scores better than the baseline. No adverse reactions were found. Conclusion Poly-L-lactic acid injection has a good effect on improving the depression of lower eyelid after external blepharoplasty, with higher patient satisfaction and safe application.