The invention relates to an 8-25mm thickness type low-yield-ratio and high-strength steel sheet for a tank truck. The 8-25mm thickness type low-yield-ratio and high-strength steel sheet for the tank truck solves the shortages such as high yield ratio, low welding performance and high production cost of a current steel sheet. The 8-25mm thickness type low-yield-ratio and high-strength steel sheet for the tank truck is characterized in that a C+Mn+Cr and Nb and Ni microalloying system is adopted; the steel comprises the following chemical components in percentage by weight: 0.08-0.15% of C, 0.05-0.20% of Si, 1.50-2.00% of Mn, not greater than 0.012% of P, not greater than 0.005% of S, 0.32-0.45% of Cr, 0.10-0.20% of Ni, 0.02-0.07% of Nb, and the balance Fe and inevitable impurity elements; and the formula (seeing the description) is met. A normalizing technology is carried out for production; the mechanical performance meets the condition that the yield strength is not less than 400MPa;the tensile strength Rm is not less than 600MPa; the ductility A50 is not less than 32%; the yield ratio is not greater than 0.75; the transverse impact energy KV2 at below 50 DEG C is not less than 47J; the technical processes include preparing molten iron through a blast furnace, performing KR treatment on the molten iron, performing smelting in a 120-160t oxygen converter, performing refining in an LF (ladle furnace), performing treatment (refining) in an RH vacuum furnace, performing continuous casting, heating a casting blank, performing controlled rolling, performing normalizing, detecting cracks, and inspecting. The 8-25mm thickness type low-yield-ratio and high-strength steel sheet for the tank truck has the characteristics of being low in yield ratio, high in strength, outstandingin low-temperature toughness and plasticity, and high in welding performance; and in addition, the production cost is low; and the operability is high.