<p>In proton exchange membrane fuel cells (PEMFCs), coolant flow uniformity is a key element to ensure efficient and stable operation of stacks. As the source of the coolant inflow channel, the coolant manifold structure directly affects the coolant flow characteristics. In order to improve the coolant flow uniformity in the stack, this paper proposes a novel manifold design with intervals and systematically explores the influence mechanism of interval number and interval-rib ratio on the coolant flow uniformity in PEMFC stacks by using computational fluid dynamics (CFD) numerical simulation. The results show that there is a nonlinear relationship between interval number, interval-rib ratio, and flow uniformity. When interval number is 2, the coefficient of variation of mass flow rate is 1.29%, which indicates that the coolant flow uniformity in the stack is optimal. Too few or too many interval numbers and interval-rib ratios result in non-uniform flow distribution. In terms of pressure characteristics, stack pressure drop and channel pressure drop increase significantly with increasing interval number and interval-rib ratio. Additionally, the coolant flow distribution uniformity directly determines the channel temperature uniformity. Some channels have low cooling efficiency due to large flow fluctuations, and the average temperature and temperature uniformity index are significantly high.</p>