Objective To explore the changes of HSP70 expression after radiofrequency ablation of benign thyroid nodules and to discuss the potential relevance. Methods Ultrasound-guided radiofrequency ablation (RFA) was conducted for treating 50 solid thyroid nodules in 50 patients. Three different regions of interest (ROI), namely the central region, marginal region and transitional region, were set on each nodule for quantitative investigation of HSP70 expression by using immunohistochemistry method. Each ROI experienced histological sampling by using core-needle biopsy before and after RFA. HSP70 expression was compared for the same ROI before and after ablation and between different ROIs after ablation. Results HSP70 expression had no significant changes in the central and marginal regions before and after ablation in the 50 solid thyroid nodules, and the expression was significantly enhanced in the transitional region after ablation (P<0.05). After ablation the expression of HSP70 in the transitional region was significantly higher than those in the central and marginal regions (P<0.05), with no significant difference found between the latter two regions. Conclusion Increased expression of HSP70 in the transitional region might protect normal glandular tissue against heat damage during thermal ablation treatment of benign thyroid nodules.