Phase change material thermal diodes designed on the basis of different heat transfer forms and coefficients caused by different phase transition degrees in opposite heat transfer directions are considered as potential thermal management devices. However, the use of a variety of materials or only relying on numerical simulation research makes its structure complex or idealized, which reduces the possibility of practical application. Therefore, in this work, a simple thermal diode structure containing only CaCl₂·6H₂O single-phase variable material is proposed in combination with changes in heat transfer form and heat transfer coefficient in solid-liquid phase change and natural convection process. The corresponding device is prepared, and a steady-state heat flux test system is set up for experimental study, the measured results are close to those recorded in the literature with good accuracy. The influence of the temperature difference between hot end and cold end and the direction of positive heat transfer and negative heat transfer on the thermal rectification effect of the thermal diode are studied experimentally. The results show that the heat flux of the thermal diode decreases with the decrease of the difference in temperature between the cold source and hot source, and the thermal rectification ratio reaches to 1.58 when the forward and reverse along the antigravity direction and gravity direction, respectively. The optimal cold source temperature range is 20–25 ℃, which is close to room temperature. The proposed phase change material thermal diode structure has a certain application potential in energy saving and thermal management of building.