The battery thermal management (BTM) system is necessary for electric vehicle (EV) to maintain the temperature of batteries. In order to enhance the cooling performance of BTM, the Al2O3-water nanofluid is employed and a lattice Boltzmann (LB) model for cylinder BTM is established. The validation of BTM numerical model has been conducted by solving the problem of a hollow cylinder with a uniformly distributed heat source. The cooling performances for one-battery and 5-batteries system have been investigated and the simulation results show that the nanofluid based BTM is able to maintain the temperature. Furthermore, for 5-batteries system, adding the nanoparticles can enhance the cooling performance and decrease the average temperature of battery effectively. Compared to the water based BTM, the average temperature of battery has been decreased by 7% with volume fraction as 0.04. Moreover, for the nanofluid with high volume fraction, increasing the Reynolds number will decrease the average temperature of battery, and make the standard deviation of battery temperature and maximum temperature larger in the meanwhile. The simulation results will be helpful to the design of nanofluid BTM system. (C) 2015 Elsevier Ltd. All rights reserved.