Abstract: Combined with a deep-buried U-bend pipe heat exchange system with a depth of 2505 m in Xi’an,a three-dimensional fullsize numerical model was established on the basis of in-situ experimental verification,and the effect of the heat flow carrier type on heat transfer enhancement of the buried pipe was simulated and analyzed. In addition to the conventional water,three nanofluids,Al₂O₃/water,CuO/water and SiO₂/water,were also selected as the heat flow carriers in the buried pipe. By changing the volume concentration of nanoparticles of the three nanofluids to 0.1%,0.3%,0.5% and 1%,respectively,the influence of the types of nanofluids and the volume concentration of nanoparticles on the heat transfer of buried pipes was analyzed. The research results shown that in terms of the heat transfer of the entire buried pipe,the enhanced heat transfer effect of the nanofluid is very small. Therefore,it is not efficient and reasonable to change the heat flow carrier of the buried pipe to achieve the enhanced heat transfer of the buried pipe.