Sloping baffle plates are installed numerically in the flow channel of proton exchange membrane fuel cell (PEMFC) to promote the mass transport in the porous electrode and the fuel cell performance. The sloping angle of baffle plate on the mass transport and performance of PEMFC are investigated and optimized. The numerical results show that the sloping angle of baffle plate influences the velocity distribution, flow resistance in the flow channel, and the intensity of mass transport between the channel and porous electrode. Larger sloping angle increases the velocity in the vertical direction which brings stronger squeeze effect between the channel and porous electrode, but it also reduces the squeeze area and increases the flow resistance. An optimization for the sloping angle of baffle plate is carried out. The baffle plate with the sloping angle of 45 degrees shows the best performance in PEMFC net power considering the pumping power caused by the pressure loss. The effect of the baffle plate number is also investigated and optimized. The fuel cell current density increases with the baffle plate number, but the increment rate is decreased. The pumping power increases almost linearly with the baffle plate number. The PEMFC with six sloping baffle plates installed in the channel is found to be optimal in terms of the net power.