Abstract: Accurate characterization of specific absorption rate (SAR) is critical to the temperature field simulation of constant-power microwave ablation (MWA). In this paper, a single-needle feedback method for SAR during 2 450 MHz MWA was proposed and a temperature field simulation technique based on SAR feedback was implemented. The spatial distribution functions of SAR were first obtained from the ex vivo porcine liver experiments. Second, the accurate characterization forms of SAR with temperature were acquired according to the single-needle measurements. Finally, temperature field simulation using SAR feedback was carried out to verify the temperature prediction accuracy. The experimental results show that the simulation data is in good agreement with the measured temperatures. For the verification points, the average maximum temperature error is about 2.805 ℃, the average temperature error is about 1.551 ℃ and the standard deviation is about 1.121 ℃. In conclusion, the temperature field simulation based on SAR feedback can effectively predict the temperature distributions during the MWA process, and thus provide a reliable reference for clinical MWA surgery.