The pressing force of the gear oil pump packing on the shaft is generated by tightening the gland bolts. Since the filler is an elastoplastic body, when subjected to axial compression, friction is generated to cause the pressing force to gradually decrease in the axial direction, and the resulting radial pressing force causes the filler to abut against the shaft surface to prevent the medium from leaking out. The distribution of the radial pressing force is from the outer end (gauge) to the inner end, firstly sharply decreasing and then flattening. The distribution of the medium pressure is gradually decreased from the inner end to the outer end. When the external medium pressure is zero, the leakage is very high. Less, greater than zero, the leakage gear oil pump packing seal is filled in the stuffing box by the packing, and the packing is pressed against the surface of the shaft through the packing gland. Since the surface of the shaft is always rough, it can only partially fit with the filler, while the part is not in contact, which forms numerous labyrinths. When the pressurized medium passes through the surface of the shaft, the medium is throttled multiple times, and the "maze effect" is used to achieve the seal. The sealing and friction of the filler and the surface of the shaft are similar to those of the sliding bearing. The solid should have sufficient liquid for lubrication to ensure a certain life of the seal, the so-called "bearing effect". This shows a good packing seal, which is a combination of the labyrinth effect and the bearing effect.