Objective To evaluate the safety and effectiveness of ultrasound-guided percutaneous thermal ablation in the treatment of low-risk unifocal papillary thyroid microcarcinoma (PTMC). Methods Patients with single-focal PTMC admitted to the 928th Hospital of the PLA Joint Logistic Support Force from June 2017 to June 2019 were selected, and ultrasound-guided percutaneous thermal ablation therapy was performed. The extent of ablation was assessed with contrast-enhanced ultrasound immediately after thermal ablation, and the ablation area, and thyroid function were measured for clinical evaluation at 1, 3, 6, 12,and 18 months, respectively. Clinical evaluation was performed at 1, 3, 6 and 12 months after thermal ablation. Results A total of 214 patients with PTMC were included, including 62 males (29.0%) and 152 females (71.0%), aged 17-77 (44.1±13.1) years old.The maximum diameter of the tumor was 0.2-1.0 (0.59±0.18) cm. The patients were followed up at 1, 3, 6, 12 and 18 months after thermal ablation, the follow-up time was 12-18 (15.14±3.01) months. After the initial thermal ablation, the maximum diameter of the ablated area was (1.372±0.440) cm, and gradually decreased to (1.108±0.438) cm, (0.753±0.440) cm, (0.483±0.324) cm,(0.162±0.205) cm, and (0.047±0.140) cm. After initial thermal ablation, the volume of ablated lesion was (1.083±1.819) cm³, and gradually decreased to (0.606±1.259) cm³, (0.273±0.784) cm³, (0.069±0.154) cm³, (0.006±0.156) cm³, and (0.001±0.004) cm³.The volume reduction ratio (VRR) at 1, 3, 6, 12 and 18 months after thermal ablation was 0.457±0.218, 0.837±0.150,0.943±0.090, 0.994±0.012, 0.999±0.002. There was a significant difference in VRR between every two follow-up visits (P<0.001).The thyroid function test results of patients before and 1 month after thermal ablation were normal, and there were no statistically significant differences (P>0.05). During the follow-up period, no tumor regrowth, local recurrence or distant metastasis was found.The most common complication was mild pain (31.8%, 68/214). Some patients developed toothache, sub-mandibular radiation pain and unilateral headache during ablation, and the pain symptoms were relieved immediately after ablation. All local pain symptoms were relieved 24-48 h after thermal ablation without treatment. Conclusions Ultrasound-guided percutaneous thermal ablation for the treatment of low-risk PTMC is safe and effective. It has less trauma and fewer complications, and can preserve the patient's thyroid function. This is a safe and effective alternative strategy for the treatment of low-risk PTMC, especially for patients who are not suitable for surgical treatment.