This study presents a novel composite magnetic field ferrofluid seal (CMFS) for high-pressure hydrogen energy applications. The CMFS seal integrates four strategically positioned permanent magnets with alternating polarities, in order to enhance magnetic flux intensity and steep gradients within multiple sealing stages. A two-dimensional axisymmetric finite element model was established to analyze the magnetic flux distribution. While sealing performance was theoretically evaluated using a modified Bernoulli equation. The parametric analysis and structure optimization were conducted on the seal performance using response surface methodology (RSM) of geometric parameters, such as pole tooth height, slot-to-tooth width ratio, axial width of boundary magnets, and radial thickness of inner magnets. The results indicated an average 23.89% enhancement in the pressure resistance, compared with the traditional structures. In addition, the optimized CMFS was achieved a 26.07% improvement over its initial configuration. These findings provide theoretical and practical guidelines to advance the ferrofluid seal design in hydrogen energy and fuel cell systems.