An experiment system for CPU cooling based on nanofluids is set up. The flow and heat transfer characteristics of TiO2-water nanofluids in CPU heat sink are experimentally investigated. The influences of rectangular groove depths (1 mm, 2 mm) and cylindrical bulge arrangement modes (aligned and staggered arrangements) on thermo-hydraulic performances of CPU cooled by TiO2-water nanofluids are analyzed. In addition, the influences of nanoparticle mass fractions (0.0%, 0.1%, 0.2%, 0.3%, 0.4%, 0.5%) and Reynolds numbers (472-1198) are studied. The thermal efficiency and exergy efficiency evaluation plots are developed and are applied to evaluate the thermo-hydraulic performance of nanofluids. It is found that large depth rectangular groove and staggered arrangement cylindrical bulges are beneficial to heat transfer enhancement. Nanofluids with mass fraction of 0.3% and 0.4% show the best cooling performance for rectangular grooves structure and cylindrical bulges structure respectively. CPU with rectangular grooves and cylindrical bugles shows higher exergy efficiency than that with smooth surfaces under the same pump power. The exergy efficiency is sensitive to deep grooves, aligned arrangement bulges, small Reynolds number. Nanofluids with low mass fraction (0.1%) show the highest exergy efficiency.