The invention provides high-strength low-carbon high silicon manganese molybdenum niobium system cold-rolled dual phase steel. The steel comprises the following components in percentage by weight: 0.06-0.10 percent of C, 1.51-2.0 percent of Si, 1.5-2.5 percent of Mn, 0.01-0.10 percent of Mo, 0.01-0.05 percent of Nb, less than 0.005 percent of S, less than 0.01 percent of P and less than 0.01 percent of N. The preparation method comprises the following steps: melting, continuously casting into a blank, conventionally heating the casting blank, and carrying out hot rolling; reeling; conventionally pickling and carrying out cold rolling; annealing and galvanizing; slowly cooling; overaging and cooling to room temperature. According to the dual phase steel, by adopting the low-carbon high-silicon, the purity of ferrite can be improved, and the extensibility of steel can be effectively improved; and a proper amount of molybdenum, niobium and other microalloys are added to compound and enhance, so that the strength of steel is guaranteed. The proportion of the second phase of the dual phase steel and the microscopic appearance of the second martensite can be effectively guaranteed by high-temperature annealing and low-temperature overaging treatment, so that the strength of a steel sheet can be effectively guaranteed. On the premise that the safety of a vehicle is not reduced, the tensile strength of the steel is increased to over 800MPa, and the ductility A80mm is more than 18 percent, and the development requirement for light weight and high enhancement of vehicles can be met.