In this paper, pumping of water-based magnetic nanofluid of Fe₃O₄ by the Kelvin force due to the non-uniform magnetic field inside the microchannel with hydrophobic walls is numerically studied. The magnetic field of permanent magnet is used as a magnetic source. The governing equations are derived from the addition of the Kelvin body force to the momentum equations, which are discretized by the finite volume along with PISO algorithm. To study the parameters affecting the performance of the magnetic nanofluid micropump, slip length of walls, the nanoparticle diameter, volume fraction of the nanoparticles, saturation magnetization of magnet, and width and height of the horizontal and vertical magnets are changed. The results show that increasing each of these parameters leads to an increase in the speed of the flow in microchannel, which is due to the increase in the Kelvin force along the channel. The effect of diameter of the magnetic nanoparticles on the speed of generated flow inside the channel was greater than that of the other parameters. In addition, the vertical magnet causes more speed than the horizontal one. Thermal characteristics of magnetic nanofluid flow have been also investigated by calculation of the temperature in outlet of microchannel. There is a slight increase in temperature due to small effect of magnetocaloric and viscous dissipation effects.