Magnetic fluid is a new kind of functional material. As one of its important applications, magnetic fluid seals have widely served as the non-contact seals in mechanical devices, due to their advantageous properties. However, the experimental performance can be confined to the inaccurate predictions in the pressure resistance during loading. This study presents a systematic simulation of the pressurization in a multi-tooth magnetic fluid seal that characterized by a small tooth pitch. The results demonstrate that the flow dynamics can result from the bidirectional pressure transfer, and then couple with the reduction in magnetic fluid volume, leading to the lower pressure resistance of the magnetic fluid seal, compared with theoretical value. This finding can provide one guidance to predict the pressure resistance of magnetic fluid seals.