Disclosed are a high-strength and high-toughness steel plate with an 800 MPa grade tensile strength and a method for manufacturing the same, the chemical composition of the steel plate in weight percentage being: C: 0.15-0.25%, Si: 1.0-2.0%, Mn: 1.2-2.0%, P≤0.015%, S≤0.005%, Al: 0.5-1.0%, N: ≤0.006%, Nb: 0.02-0.06%, O≤0.003%, and the balance being Fe and other inevitable impurities, and 1.5%≤Si+Al≤2.5%. By adopting an isothermal heat treatment a high-strength and high-toughness steel plate with an 800 MPa grade tensile strength, which has a microstructure mainly including bainite ferrite and residual austenite, is obtained impact energy.