Objective: To evaluate the safety and efficacy of mini-flank incision for open partial nephrectomy for stage T1b renal tumor. Methods: The data of patients with stage T1b renal tumor who underwent mini-flank incision for open partial nephrectomy between January 2010 to September 2015 were retrospectively reviewed. The Nephron-sparing surgery (NSS) was performed through mini-flank supra-12th rib incision under general anesthesia. Results: A total of 47 patients(31 male and 16 female) were enrolled in our study. The median age was 40 years (range 22-67 years). The Zhongshan Score(ZS score) of renal tumors was 6 in 5 cases, 7 in 13 cases, 8 in 12 cases, 9 in 5 cases, 10 in 6 cases, 11 in 2 cases, 12 in 2 cases, 13 in 2 cases. The length of incision was from 7 cm to 9 cm, with an average of 8.1 cm. The operative time was from 70 min to 150 min, with an average of 96 min. The blood loss was from 50 ml to 600 ml, with an average of 135 ml. The warm ischemia time was from 20 min to 35 min, with an average of 28 min. All of the surgery margin were negative. One patient had fluid in surgical region and relieved after the drainage, and one patient had acute myocardial infarction. The hospital stay time was from 5 d to 14 d, with an average of 8 d. The pathological diagnosis included clear cell carcinoma in 37 cases, multilocular cystic renal carcinoma in 1 case, chromophobe cell tumor in 4 cases, and papillary carcinoma in 5 cases. The mean preoperative serum creatinine level was 87 μmol/L(48-150 μmol/L) and with a mean of 91 μmol/L(52-148 μmol/L) at 3 month follow-up after surgery, and there was no difference between the preoperative and postoperative period(P>0.05). A total of 45 out of 47 patients were followed up for 36 to 78 months, with an average of 60 months, and no one had recurrence or metastasis during follow-up. Conclusion: Mini-flank incision for open partial nephrectomy for renal tumor with stage T1b is safe and effective, which is worthy of promotion and application for small incision and quick recovery.