Abstract: Disclosed is a dynamic sealing device for a middle- or high-voltage power switch equipment, comprising: a housing (9), a cover (10) fitted with the housing (9), a main shaft (1) mounted within the housing (9) and coupling an acting mechanism inside an aeration compartment and an operating mechanism outside the aeration compartment, two bearings (3) for mounting the main shaft (1), and at least one permanent magnet (8) and at least two poles (5) being fitted to an inner hole of the housing (9) and having gaps between them and the main shaft (1), wherein, the two poles (5) are located on both sides of the permanent magnet (8) respectively and have a plurality of pole teeth, and magnetic fluid (7) is provided between the pole teeth of the poles (5) and the main shaft (1).