The invention provides a microcomputer-controlled automatic switching system for the economic operation of 6kV to 20kV transformers connected in parallel. The switching system comprises a current signal detection circuit, a judgement and processing circuit, a transformer closing circuit and a transformer opening circuit; the output of the current signal judgement and processing circuit is provided with two terminals for a large fixed value and a small fixed value, which are respectively connected with the transformer closing circuit and the transformer opening circuit; when the current signal detection circuit detects that the current values of the transformers exceed the set large fixed value, the closing circuit is delayed to start up, and one transformer is automatically closed to operate; when the set small current values of the transformers are detected, the opening circuit is delayed to start up, and the operation of one transformer is automatically stopped. By utilizing the microcomputer technology, the switching system can accurately and automatically carry out switching in time according to power consumption load and the set economic operation mode of the transformers, so that the operation loss of the transformers can be reduced, the switching system can be used for the economic operation of a plurality of transformers connected in parallel and the operation of child and mother transformers, the complex, burdensome switching operation and misoperation of workers can be avoided, safety and reliability are enhanced, and the loss of a power grid is effectively reduced.