Background: Small lung metastases move with respiration, making localization difficult and often increasing the number of puncture. Accurate puncture can reduce trauma to lung tissue and accelerate patient recovery.Objective: To present our experience with the technique of using a local anesthesia 5-ml syringe as a guide for computerized tomography (CT)-guided iodine-125 seed implantation (CT-ISI).Methods: This was a retrospective study of patients with small metastatic tumors in the lung treated with CT-ISI between 12/2013 and 03/2018 at the Affiliated Hospital of the University. The patients were divided according to whether a 5-ml syringe was used as a guide during CT-ISI or not. The final follow-up was on March 31st, 2018. Implantation success and complications were examined.Results: Nineteen patients were included. A total of 840 seeds were used, with 44.2±33.6 (range, 10-160) seeds per patient. The mean D90 for CT-ISI was 134.5±7.5 Gy. Treatment intervention for eleven patients was performed using a 5-ml syringe as a guide during CT-ISI. There were no differences in total dose and number of implanted seeds between the two groups, but the number of punctures per lesion was lower in the syringe group than in the no-syringe group (1.9±0.5 vs. 2.9±0.6, P<0.001), suggesting a higher puncture accuracy. One patient in the no-syringe group experienced grade 2 chest tightness, chest pain, intraoperative needle tract bleeding, and postoperative blood in sputum.Conclusion: Puncture with a 5-ml syringe as a guide during CT-ISI is probably a more accurate option for patients with small (<2.5 cm) lung metastasis.