A large-size transformer comprises a transformer box body, a transformer sleeve, an ascending seat, a hoop and at least two support strips, wherein the ascending seat is fixed at the top of a side surface of the transformer box body, a plurality of reinforcement plates and a plurality of reinforcement ribs are respectively arranged at the top and the size surface of the transformer box body and are uniformly arranged in parallel, the transformer sleeve is fixedly connected with the ascending seat, the hoop sleeves and is fixed on the ascending seat, two ends of each support strip are respectively connected with the hoop and the reinforcement plates or reinforcement ribs so that limited support is formed on the ascending seat. The large-size transformer has the advantage that the vacancy ofa seismic reinforcement method or measure of the ascending seat of a current large-size transformer is made up.