A pressure protection device includes a housing, a sliding block, and an adjusting block. The housing includes a receiving chamber communicating with a seal chamber and the housing defines a first gas hole and a second gas hole each communicating the receiving chamber to an ambient environment. The sliding block divides the receiving chamber into a first space and a second space and defines a through hole communicating the first space with the second space. The adjusting block is located in the first space and configured to be attracted to the sliding block so that the through hole is selectively blocked by the adjusting block. When the sliding block slides in the receiving chamber, the first gas hole is selectively blocked by the sliding block to isolate from or to communicate with the first space, and the second gas hole always communicates with the second space.