The invention relates to a new technology for the noise treatment of a large-sized converter transformer by using a firewall and a valve wall at two sides of the converter transformer to carry out closed acoustic treatment to a main body of the transformer. The main body of the transformer is placed in a 'BOX'. In order to provide convenience for examining and repairing equipment, a self supporting sound insulation and absorption compound structure is adopted in both a 'BOX-IN' front board and a 'BOX-IN' top board. As partial sound insulation and absorption boards and steel frames can not be disassembled, all nodes are connected by bolts, thus being assembled and disassembled rapidly. All parts are manufactured by molding, do not require cutting on site and have high processing and reusing rate.