The invention relates to the technical field of transformer breathing device, and provides a transformer breather. The transformer breather comprises a flange plate, a breather top cover, a connection rod, a breather shell, a transparent bottom cover and an oil cup, wherein the flange plate is integratedly connected with the breather top cover, a feeding hole is formed in the breather top cover, a detachable plug is arranged on the feeding hole, the breather shell is fixedly installed with the breather top cover, a horizontal baffle plate is arranged at a lower end of the breather shell, a sleeve is sleeved at an outer edge of the horizontal baffle plate, a breathing sleeve is fixedly arranged at a bottom part of the horizontal baffle plate, an isolation layer mesh wraps a bottom part of the breathing sleeve, a round hole is formed in a middle part of the isolation layer mesh, the isolation layer mesh is detachably fixed on the breathing sleeve along the circumference, and the oil cup is fixedly arranged on an inner wall of a lower part of the sleeve. The transformer breather is reasonable and compact in structure and is not needed to be integratedly disassembled by employing a buckle structure, the silica gel replacement time is effectively shortened, the heavy gas protection withdraw time of a main transformer is reduced, and the safety running condition of the main transformer is improved.