Nanofluids have attracted more and more concerns own their excellent heat transfer performance in comparison with conventional fluids. In this paper, a reverse non equilibrium molecular dynamics method is presented to analyze the enhanced thermal properties of Cu-Ar nanofluids. It is found that the thermal conductivity of Cu-Ar nanofluids is sensitive to particle size and volume fraction. Meanwhile, the micro-mechanism of the enhancement of thermal conductivity of Cu-Ar nanofluids is analyzed. The results reveal that the nanofluids have some similar microstructure characteristics as crystals. The nanoparticles are more likely to adsorb liquid molecules influenced by the solid-liquid interactions. (C) 2019 Elsevier B.V. All rights reserved.