The present invention relates to a binary compound synergistic herbicide containing mesotrione A and a herbicide B, and is used for settling the insufficiencies of single function, inferior effect, large residual quantity, etc. of herbicide in the chemical prevention of weed of the corn field, wherein, A is mesotrione, and B is one chemical selected from B1 of 2,4-D, B2 of 2,4-D sodium, B3 of 2,4-D ethyl, B4 of 2,4-D butyl, B5 of 2,4-D isoctyl, B6 of 2,4-D dimethylamine, B7 of 2-methyl-4-chloro-phenoxyacetic acid MCPA, B8 of MCPA sodium, B9 of MCPA ethyl, B10 of MCPA butyl, B11 of MCPA isoctyl, and B12 of MCPA dimethylamine. The binary combination synergistic herbicide used for preventing weed of the corn field according to the invention contains 1-99 weight parts of mesotrione A and herbicide B and conventional herbicide adjuvant and/or carrier. The binary combination synergistic herbicide according to the invention has the effects of high weed killing effect, broad weed killing spectrum, high safety to the corn, no side effect, no influence to the flowing crop and low use cost.