A high-strength high-elongation tinned primary plate and a double cold reduction method therefor. The tinned primary plate comprises the following components by weight from 0.065 to 0.12% of carbon, from 0.2 to 0.8% of manganese, from 0.003 to 0.015% of nitrogen, the remainder being iron and the inevitable trace impurities. The tinned primary plate is necessarily subjected to double cold reduction at a reduction of 5˜13% and a rolling tension of 50˜100 MPa. The tinned primary plate has a yield strength of Rp0.2≥520 MPa, and percentage elongations in rolling direction RD, 45° direction and perpendicular direction TD, which are all greater than or equal to 10% after bake-hardening.