The structural load for transmission lines continually increases and application of large angle steels in UHV tower will become inevitable. The paper analyses the feasibility technically and economically for large angle steels replacing normal ones. In addition, the effects of purchase price variances between large angle steels and normal ones on the economy of transmission lines are discussed. Combined with the construction scale of power grid during the 12th Five-Year-Plan period, the factors affecting the large angle steel application, the applicable amount and economic-social benefits are demonstrated in the next five years.