The invention relates to an EI type surge (impact) anti-interference and overvoltage anti-interference low-frequency power supply transformer and a machining process. Five layers of polyester enameled wires with the total flux of 170 Ts are wound around a G-shaped framework to form a primary winding; five layers of polyester enameled wires with the total flux of 82 Ts are wound around the surface, where two layers of NOMEX insulating paper I and two layers of polyimide insulating adhesive tape are arranged in sequence in a between-section insulation mode, of the primary winding in a two-wire parallel mode to form a secondary winding, and two layers of NOMEX insulating paper II wrap the surface of the secondary winding; a plurality of E-shaped iron cores are correspondingly overlapped and inserted in holes of the G-shaped framework, and a plurality of I-shaped iron cores are arranged in notches which are each formed by inserting the two corresponding E-shaped iron cores oppositely; a metal support, the iron cores, a primary ground electrode and a secondary ground electrode are fixed together through four bolts; the start ends, the stop ends, the primary ground electrode and the secondary ground electrode of the primary winding and the secondary winding are fixedly connected to a terminal block I and a terminal block II of two beams respectively, and finally the whole is coated with a layer of antirust paint. The transformer has the advantage that the surge prevention level in a low-frequency transformer circuit can be improved without using external devices.