Objective: To compare the ablation features and variations among microwave ablation (MWA), radiofrequency ablation (RFA) and laser ablation (LA) in pig thyroid in vitro, so as to provide reference for clinical decision-making. Methods: One hundred and fifty freshly harvested pig thyroid glands were equally divided into 3 groups, and then underwent MWA (20 W 5 min), RFA (5 W) and LA (3 W 1200 J), respectively. In each group, the real-time temperature at the target area was measured and real-time ultrasound observation was conducted during ablation procedure, and after ablation, the specimens were cut open along the needle passage, and the gross appearance was observed, ablation volume was determined and pathological examination was performed. Results: Comparison among the three groups showed that the ablation volume was largest in MWA group (1 597.09 mm3), followed by LA group (780.89 mm3), and was smallest in RFA group (162.20 mm3), and the difference between either of them had statistical significance (all P<0.05). The temperature rise curve of MWA or RFA was swift and steep, and that of LA was gentle and long, but its maximum temperature was highest (200.9 ℃ ). In ablation zone, no evident tissue destruction as well as carbonization and vaporization cavity was seen in RFA group, carbonization but no vaporization cavity was found in MWA group, and both carbonization and vaporization cavity presented in LA group. The ablation lesion from inside to outside presented coagulation necrosis and congestion reaction zone in RFA group, was carbonization, coagulation necrosis and congestion reaction zone in MWA group, and was vaporization cavity, carbonization, coagulation necrosis and congestion reaction zone in LA group, respectively. Conclusion: The ablation scope, temperature rise curve and pathological changes in the ablation zone are different among MWA, RFA and LA, and understanding their characteristics may be helpful to the rational use of these three ablation techniques.