The invention discloses 690MPa-stage anti-seismic fire-proof weather-proof building structure steel and a preparing method thereof. The steel comprises, by weight percent, 0.05 to 0.10% of C, 0.01 to0.30% of Si, 1.0 to 1.4% of Mn, 0 to 0.01% of P, 0 to 0.002% of S, 0.01 to 0.5% of Mo, 0.01 to 0.05% of Nb, 0.01 to 0.03% of Ti, 0 to 0.06% of V, 0.4 to 1.0% of Cr, 0.3 to 0.4% of Cu, 0.3 to 0.4% of Ni, 0 to 0.003% of B, 0.001 to 0.08% of N and the balance Fe and inevitable impurities. The preparing method comprises the steps of steel making, refining, continuous casting, steel blank heating, two-stage controlled rolling and controlled cooling and heat treatment. On the premise that the use property meets GB/T 19879 building structure steel plate needs, the yield strength is larger than or equal to 706 MPa, the yield ratio is smaller than or equal to 0.849, DNH coefficient is larger than or equal to 6.5%, at the temperature of 600 DEG C, heat preservation is carried out for one to three hours, the yield strength is not lower than 2/3 at the room temperature, meanwhile, the anti-seismic fire-proof weather-proof needs are met, and the property is excellent.