Objective To explore the effect of lateral thoracodorsal fat fasciocutaneous flap transfer method in defect repair after breast conserving surgery for breast cancer (BC). Methods A total of 78 patients with BC who underwent breast conserving surgery in our hospital from March 2020 to December 2022 were selected and divided into study group and control group by random number table method, with 39 patients in each group. The control group was treated with latissimus dorsi flap repair, and the study group was treated with lateral thoracodorsal fat fasciocutaneous flap transfer method. The breast aesthetics, perioperative indicators, quality of life and complications were compared between the two groups. Results The postoperative Vancouver Scar Scale (VSS) score of the study group was lower than that of the control group (P<0.05). The operation time and hospitalization time of the study group were shorter than those of the control group, and the intraoperative blood loss was less than that of the control group (P<0.05). The scores of World Health Organization Quality of Life Scale (WHOQOL-BREF) in the two groups after operation were higher than those before operation, and the scores in the study group were higher than those in the control group (P<0.05). The incidence of complications in the study group was 5.13%, which was lower than 23.08% in the control group (P<0.05). Conclusion The lateral thoracodorsal fat fasciocutaneous flap transfer method in patients with BC breast conserving surgery can improve the breast aesthetics of patients, improve perioperative indicators, improve their quality of life, and reduce complications.