The invention relates to the technical field of electric power engineering, in particular to an automatic voltage stabilizing transformer. A secondary winding of a first single-phase transformer body and a secondary winding of a second single-phase transformer body are in series connection between two power output ends; a first phase power input end, a second phase power input end and a third phase power input end are multiple points and are switched in a primary winding, wherein the point with the largest number of loops is the number of coils required when the voltage works normally. The automatic voltage stabilizing transformer has the advantages that a voltage switching circuit is simple, voltage is output stably in the voltage raising or lowering process, and the circumstance of voltage leap or outage cannot be caused.