The recommended thermal conductivity of a water solution with free convection (100 W m 1 K 1) for predicting temperatures of conventional external heating was found to be unsuitable for microwave heating due to the dielectric heating characteristic. This value was finally adjusted to 300 (W m 1 K 1), which made the prediction match the experiment very well. On this basis, the predicted spatial temperature profiles and surface temperature distributions of the fish sample also showed good agreement with the experimental results.