Method for preventing and killing weeds in direct sowing rice field

The invention relates to a method for preventing and killing weeds in a direct sowing rice field. The method comprises the step of scattering weeding macrogranules when a water layer in the rice fieldis kept at 3-4.5cm; the weeding macrogranules contain the following components in parts by weight: 10-25 parts of a weed killer, 1-25 parts of a surfactant, 2-30 parts of an oil substance, 1-10 partsof white carbon black, 10-80 parts of a solid core material and 1-30 parts of KCl, wherein the surfactant is a composite surfactant of sulfonate lignin and alkylphenol polyoxyethylene ether in a weight ratio ranging from 1:20 to 30:1; and the oil substance is a composite oil substance of mineral oil and plant oil in a weight ratio ranging from 1:10 to 20:1. The method provided by the invention has the advantages that a specific surfactant is selected, especially the surfactant is greatly improved in a specific proportion, diffusion rate is high and is higher than 1.4m/min, and loss of activeingredients is reduced to b