OBJECTIVE The study summarizes the effectiveness of ultrasound-assisted microsurgical left spermatic-inferior epigastric vein anastomosis for treating nutcracker syndrome (NCS)-associated varicocele. METHODS Cases of NCS-associated varicocele were recruited between December 2012 and December 2018. Prior to the operation, all patients were tested for the internal diameter and blood flow velocity of left renal vein, testicular volume, maximum venous diameter and venous retrograde flow in the pampiniform plexus of veins during the Valsalva maneuver by Color Doppler ultrasound. Moreover, the direction of left spermatic and inferior epigastric vein was marked. RESULTS All patients underwent ligation of the internal spermatic veins and left spermatic-inferior epigastric vein anastomosis under microscopy. Color Doppler ultrasound, urinary and semen analysis (above age 18 years old) were reviewed during the follow-up period. 53 patients (94.6%) underwent spermatic-inferior epigastric vein anastomosis with the mean operation time of 78.4 ± 14.2 min. The hospital stay was 4-7 days. Scrotal hydrocele, wound infection and testicular atrophy did not occur after operation. However, there were 5 cases of left varicocele recurrence and 2 cases of vascular anastomotic thrombosis. 51 cases had decrease in blood peak flow rate of left renal vein and improvement in nutcracker syndrome while scrotal bulge symptoms resolved in 26 cases. 10 cases had microscopic hematuria disappearance with symptom improvement in 2 cases. 19 cases of left testicular hypotrophy experience no further deterioration after surgery, of which 16 cases had catch-up testicular growth. CONCLUSIONS Ultrasound-assisted microsurgical left spermatic-inferior epigastric vein anastomosis assisted is safe, easy and effective for treating nutcracker syndrome-associated varicocele.