OBJECTIVE To evaluate the clinical efficacy of microscopic internal spermatic-inferior epigastric vein anastomosis in the treatment of left varicocele and compare it with microscopic spermatic vein ligation for the same condition. METHODS A retrospective analysis of 74 patients with left varicocele between July 2020 and July 2022 was performed. The patients were divided into two groups based on the surgical method used. Group A consisted of 37 patients who underwent microscopic internal spermatic-inferior epigastric vein anastomosis, while Group B consisted of 37 patients who underwent microscopic spermatic vein ligation. Comparison of preoperative and postoperative semen quality, reproductive hormone levels, scrotal ultrasound results, duration of surgery, length of hospital stay, postoperative recurrence rate, and occurrence of complications with a follow-up time of 12 mo between two groups. RESULTS Both groups showed significant improvements in semen quality and serum reproductive hormone levels. The Group A demonstrated significantly improved sperm forward motility compared to Group B, but had longer operation times and hospital stays (P < 0.05). After 1 year of follow-up, 8 partners in Group A and 6 partners in Group B achieved natural conception, with no significant difference between the two groups. There were no recurrences observed in either group during the follow-up period, and no significant statistical differences were found in other postoperative observation indicators. CONCLUSIONS Both microscopic internal spermatic-inferior epigastric vein anastomosis and microscopic spermatic vein ligation are effective surgical methods for treating left varicocele. Anastomosis surgery provides greater improvement in sperm motility, although it is associated with longer operation times and hospital stays.