The present invention relates to a high-performance fire-resistant weather-resisting building steel and its production method. Said invention steel contains C, Si, Mn, P, S, Mo, Ti, Al, N, O, Cr, Ni, Cu, Ca, B and one or more than one kind of Nb, V and RE and the rest is Fe. After having been undergone the processes of smelting, rolling and heat treatment, said building steel possesses high strenght, high toughness and excellent fire-resisting and weather-resisting properties. The building steel can be used for providing various steel structural members whose thickness is 4-100 mm in the fields of building, civil engineering and marine structure. Under the large linear energy (50-100 kJ / cm) welding condition of gas-arc welding, electroslag welding and high-frequency resistance welding, its heat affected zone (HAZ) still possesses excellent toughness so as to greatly raise welding efficiency of engineering structure and reduce its manufacture cost.