The invention provides an automatic flushing device of a transformer cooling system, and belongs to the field of washing devices of transformer cooling systems. The automatic flushing device comprises a transformer, and the transformer is provided with the cooling system. The automatic flushing device is provided with a horizontal fixed rod, a vertical movable rod, bent boards, a motor II, a motor I, a chain I, a chain, a gear, a cross-shaped pinch plate, an air blast sprayer, a horizontal pressing plate, a vertical rod moving track, a fastening screw, a travel switch, a centre and a control cabinet, wherein the horizontal fixed rod is fixed to the cooling system of the transformer through the two bent boards, the motor I and the gear are fixed to the two ends of the horizontal fixed rod respectively, the part, between the motor I and the gear, on the horizontal fixed rod is provided with the cross-shaped pinch plate, and the large plane of the cross-shaped pinch plate is provided with the horizontal track. The flushing efficiency is high, manual work is not needed, and labor force is greatly saved.