In order to improve the simulation accuracy, this paper took potatoes as examples, selected two irregular-shape potatoes, used a three-dimensional scanner to obtain the accurate geometries, imported the geometries into a multiphysics finite element software COMSOL Multiphysics^, solved its temperature distribution field under different powers/voltages, and carried experiment verifications. Results show that after 40 minutes of RF heating, the temperature distribution, maximum and minimum temperature values and internal time-temperature curves of the simulated results are in good agreement with the experimental results with a simulation accuracy over 90%. This method is suitable for simulating RF heating processes of irregular-shape samples. Variations of sample shape and plate voltages do not have significant influence to the accuracy of RF heating simulation.