The invention relates to a pressure monitoring and warning system in a breather of a transformer. The pressure monitoring and warning system comprises a positive pressure gauge, a negative pressure gauge, a pressure release valve, a small silica gel tank, a connecting pipe and a rainproof cover, wherein the rainproof cover is fixed to a breather pipe; the negative pressure gauge, the small silica gel tank and the connecting pipe are all connected to the interior of the rainproof cover; one end of the connecting pipe is closed; the other end of the connecting pipe is connected with the breather pipe; the connecting pipe is connected with the positive pressure gauge, the negative pressure gauge and the small silica gel tank respectively; the pressure release valve is further arranged above the small silica gel tank. According to the pressure monitoring and warning system in the breather of the transformer, the positive-negative pressure in a breathing system can be reflected; air can be filtered through the small silica gel tank, and the pressure can be released through the pressure release valve, so that safe operation of the transformer is ensured.