In order to study the characteristics of the temperature field of the heating system in a washer-dryer, a numerical model to compute airflow field and temperature field is established according to the theory of fluid-solid coupled heat transfer. Simulation is realized based on the finite element method and verified with tests. The simulation results are in good consistency with the test result on the three aspects of temperature distributions, ranges and fluctuation tendencies. The errors of the lowest, highest and average temperature are all within 5.38%. Influencing factors leading to the offset of the high-temperature region in the downstream heating channel can be found from the valid simulation and they can provide theoretical basis for further optimization. The simulation results show that the configuration of the part of channel between the volute tongue and the heater leads to the transverse offset, and the triangular hump leads to the longitudinal offset.