In order to solve the problem of poor heat storage capacity of traditional thermal insulation materials, the author proposed a building thermal simulation study of PCM wall under smart home buildings. The author chose urea-formaldehyde resin microcapsule with 60% mass fraction of paraffin as the research object, and gave the structure of the study wall. After determining the physical parameters of PCM, the phase change wall is simulated and analyzed, and the simulation results are compared with the experimental results used to verify the accuracy of the model. The internal temperature of phase change wall and reference wall, and the internal and external wall temperature of four-way wall were compared and analyzed by using the simulation results. The results show that the internal wall temperature of the reference wall in four directions increased with time after the 54th hour, reached the peak temperature at the 65th hour, and then the internal wall temperature decreased with time, however, the internal wall temperature in four directions began to rise with time after the 56th hour of phase transition wall, and decreased with time after the 70th hour, this indicates that there is always hysteresis of temperature rise/fall in the inner wall of PCM wall, indicating the thermal inertness of PCM heat transfer. The changes of exterior wall temperature are similar to that of exte­rior wall temperature. With the increase/decrease of outdoor temperature, exterior wall temperature increases/decreases. However, the PCM exterior wall temperature curve is higher than the reference wall (ordinary gypsum layer) inside the wall temperature curve, indicating that the PCM exterior wall temperature is higher than the reference wall exterior wall temperature. The heat transfer between inside and outside walls of building is consistent with the outdoor temperature, but the heat transfer speed of phase change wall is slow due to the heat storage function, which proves that PCM in the structure is thermal inert and capable of heat stor­age.