Abstract: The heat transfer behavior of nanofluids has many abnormal properties compared with conventional fluids.Based on the following four principles—micro-dimension effects, heat diffusion from Brownian motion, solid-liquid micro interface and particle clustering structure, the heat conduction mechanism in nanofluids was studied.A heat conductivity model of nanofluids based on the Hamilton-Crosser model and Bruggeman model was developed.By comparing with the tests of CuO-DW and Cu-DW nanofluids, the model exhibited a relatively good performance in predicting the heat conductivity of nanofluids.