Abstract: A highly stable transformer, including a first transformer, a second transformer and a current induction device. The current induction device is provided in a load line of the first transformer for detecting an induction current in the load line of the first transformer. An induction load terminal of the current induction device is connected to a control winding. The control winding is provided in a winding of the second transformer to generate an induction voltage in the winding according to the induction current value and output a voltage value matching the load. The transformer has a zero voltage deviation, can be applied to precise appliance circuits and will not produce voltage drop. The transformer adopts active loaded lines, has good operation efficiency and good stability, saves main capacitor loss of no-load and unequal loads, and improves the startup performance of the transformer to any corresponding loads in a full-load condition.