The invention relates to a herbicide composition for controlling farmland weeds, and a use thereof, and concretely relates to a binary herbicide composition used for controlling corn field grassy weeds, broadleaf weeds and Sedge weeds and treating topramezone and MCPA as active components. The topramezone: MCPA weight ratio of the composition is 1:200-2:3, and the composition can be processed to prepare any preparation form allowable in agriculture. The herbicide composition has a more substantial synergistic effect than the individual application of the above two components when the herbicide composition is used for controlling the corn field weeds, and has the advantages of weed control spectrum enlargement, control cost reduction, weed resistance generation alleviation, and good safety to crops.