The invention relates to a low-yield-ratio and high-strength steel plate having 690-MPa-level yield strength. The steel plate is prepared from chemical components including 0.10%-0.20% of C, 0.10%-0.40% of Si, 0.90%-1.40% of Mn, less than or equal to 0.030% of Nb, less than or equal to 0.010% of V, less than or equal to 0.025% of Ti, 0.02%-0.06% of Al, less than or equal to 0.10% of Ni, less thanor equal to 0.10% of Cu, 0.10%-0.80% of Cr, 0.10%-0.70% of Mo, 0.001%-0.005% of B, 0.001%-0.005% of Ca, less than or equal to 0.015% of P, less than or equal to 0.003% of S, less than or equal to 0.002% of O, less than or equal to 0.004% of N, less than or equal to 0.0002% of H and the balance Fe. The steel plate adopts the tempered sorbite and bainite duplex structure. The yield strength Rp0.2 ishigher than or equal to 690 MPa, the tensile strength Rm is higher than or equal to 770 MPa, the yield ratio Rp0.2/Rm is lower than or equal to 0.88, the ductility A is higher than or equal to 16%, and the low-temperature impact Akv at subzero 40 DEG C is higher than or equal to 100 J. The manufacturing process includes steel making by the aid of a converter or an electric furnace, LF refinement,VD or RH vacuum degassing, Ca treatment, continuous casting, heating, rolling, primary quenching, secondary quenching and tempering.