Bearing heaters are suitable for machinery manufacturing and maintenance in power plants, textile mills, papermaking, chemical industry, petroleum, machinery, mining machinery, wind power industry maintenance and other fields, and can be used as bearings, connectors, gears, mechanical bushings, etc. The workpiece is heated and demagnetized automatically, so that the cylindrical shape of the workpiece is expanded to meet the requirements of interference assembly. The current heater is controlled by a microcomputer, which enables the heater to automatically detect equipment failures, automatically adjust heater power, and soft start/stop.