Manufacturing method of economical 800MPa-grade high-plasticity steel

The invention discloses a manufacturing method of economical 800MPa-grade high-plasticity steel. The manufacturing method comprises the following steps: 1) smelting; (2) thin slab continuous casting and continuous rolling are conducted, molten steel is subjected to thin slab continuous casting and continuous rolling production, the casting blank heating temperature is 1220-1300 DEG C, rolling is directly conducted in a multi-rack finishing mill, the finish rolling starting temperature is larger than or equal to 1100 DEG C, the reduction rate of the first three passes is larger than or equal to 50%, the pass temperature is larger than or equal to 1050 DEG C, and the reduction rate of each later pass is larger than or equal to 15%; constant-speed rolling is adopted, the rolling speed is controlled to be 3.0-10.0 m/s, the finish rolling temperature is controlled to be 890-930 DEG C, and the thickness of a finished steel plate is 1.2-5.0 mm; and (3) laminar cooling is conducted, two-section type controlled coolin