Abstract: This paper presents a simulative and experimental investigation of the thermal and hydraulic fields of the TiO₂-water nanofluids with various concentrations inside a fan-microchannel heat sink. The computational method of simulation was a two-phase mixture model. The nanofluids flow and heat transfer facility which could measure flow rate,import and export of pressure drop and temperature and the temperature of heating film was set up for the experiment. Reynolds number of coolant in the microchannel was between 207 ~ 465 and the heat flux of heating film was kept in 2 × 10⁶ W / m². The results show that the relationship between the friction factor and Re of nanofluids is similar to that of water within the fan-microchannel and the friction factor is larger than that of water. The friction factor decreases while the Re increases. The heat transfer performance of nanofluids is better than that of water.Furthermore, the heat transfer enhancement of nanofluids increases with increasing Re and the concentration of nanoparticles.