An effective thermal management system that can maintain the maximum temperature and temperature difference in a desired range is needed to ensure a good performance and safety of lithium-ion batteries. In this paper, a mini-channel cooling system for high-power prismatic battery thermal management is investigated numerically using a three dimensional CFD model. The thermal performances of the cooling system when using different base fluids (i.e. water, ethylene glycol and engine oil) and their corresponding nanofluids as coolants are compared. The thermal conductivities of nanofluids are calculated using a semi-empirical correlation and the dynamic viscosities of nanofluids with different base fluids are obtained by curve fitting using experimental data. Due to its high thermal conductivity, water achieves a much better cooling effect than ethylene glycol and engine oil. However, the impact of adding nanoparticles is more remarkable for fluids with lower thermal conductivity, especially for engine oil. The nanoparticle addition is able to greatly reduce the cell maximum temperature but has a limited effect on the temperature uniformity. In addition, an evident performance enhancement is observed by increasing the suspended nanoparticles volume fractions despite that the required power cost is increased at the same time. Different influencing factors including the flow velocity and coolant inlet temperature on the mini-channel cooling performance and the enhancement of adding nanoparticles are also studied. It is observed that all of these influencing factors have significant impacts on the mini-channel cooling effects.