Purpose: To determine the factors affecting the recurrence of the solitary benign thyroid nodules (BTN) after microwave ablation (MWA).Materials and methods: Between January 2013 and January 2015, a total of 110 patients with at least one solid thyroid nodule (solid component 80%) were enrolled. MWA was performed under continuous ultrasound (US) guidance. Before and during the follow-up, the thyroid nodule volume, thyroid function and cosmetic complaints were evaluated. Recurrence is defined by the new blood flow in the total ablation area or/and >50% increase in nodule volume.Results: Almost all thyroid nodules were significantly decreased in size after MWA. After 12 months, the average volume of thyroid nodules was decreased from 12.615.1 to 3.2 +/- 5.7ml. Of the total 110 patients, 16 cases had recurrence 12 months after MWA, and these patients had a larger initial volume than that of the non-recurrence patients (11.6 +/- 14.9 vs. 23.9 +/- 12.5, p<0.01). The recurrence group also demonstrated more irregular blood vessels (1.8 8 +/- 1.1 vs. 2.8 5 +/- 1.3, p<0.05), and a lower energy (1575.5 +/- 674.3J/ml vs. 1172.3 +/- 454.2J/ml, p<0.01). In addition, 81.2% (13/16) of the patients in the recurrence group were adjacent to the vital structures, which is significantly higher than that of the non-recurrence group 28.7% (27/94) (p<0.01).Conclusions: The US-guided MWA results in a satisfactory long-term outcome of the patients with a benign solitary thyroid nodule. We identified three risk factors for recurrence: initial volume, vascularity and the energy per 1ml reduction in nodular volume.