Abstract: With the rapid consumption of fossil fuels, the issues of energy security and climate change are becoming increasingly prominent. The research of clean and sustainable energy development technology and energy storage technology has become a hot topic. By combining molecular dynamics simulation and experimental research, the influence of interface effects on the heat transport characteristics of mixed nitrate composite phase change materials (CPCM) was studied. Firstly, the thermal conductivity and specific heat capacity of CPCM were measured by laser thermal conductivity meter and differential scanning calorimeter respectively. Then Materials Studio software was used to establish the models of composite phase change materials with different NaNO₃ and KNO₃ ratios in eutectic states and different skeletons and the molecular dynamics simulation calculation of its thermal conductivity and specific heat at constant pressure was carried out. The internal mechanism of the experimental results was analyzed through the changes in radial distribution function, interface binding energy, and bulk thermal expansion coefficient, and then the competitive relationship between the interface effect and the mixed nitrate ratio on the thermal properties was further analyzed. The results show that when the mass ratio of NaNO₃ and KNO₃ is 4∶6, the interaction between ions is weaker than other ratios, and the interface binding energy and thermal conductivity are the largest. An increase in interfacial binding energy enhances the thermal conductivity more strongly than a decrease in the interaction between ions weakens the thermal conductivity, the interfacial effect plays a dominant role in the change in the thermal conductivity of CPCM. The specific heat of CPCM at constant pressure is affected by the change of ratio and skeleton material, interfacial binding energy and ionic interaction have no obvious effect on specific heat at constant pressure.