The invention provides a device for testing the pressure difference of a clean room, which can be connected with a differential pressure gauge to measure the pressure difference when in use, and has the advantages of high detection efficiency, accurate detection data and reduced possibility of polluting the clean room. The device comprises a hollow sampling joint, wherein one end of the sampling joint is provided with a connecting rod which penetrates a wall, the connecting rod is hollow and is communicated with the sampling joint, a sealing ring is further installed on one side, facing the wall, of the sampling joint, the sampling end of the connecting rod is provided with a special joint which is used for being connected with the differential pressure gauge, and a locking thread is arranged on the connecting rod and positioned on the inner side of a connecting joint; the device also comprises a sealing plate, wherein the connecting rod can penetrate the sealing plate, a sealing ringis arranged on one side of the sealing plate, which faces the wall, and a locking nut is used for locking and fixing the sealing plate and the sampling joint on the wall through the locking thread; the device further comprises a blocking device for blocking the connecting rod.