The invention discloses a herbicide spray drift preventing device for a corn field. The device comprises a liquid storage tank and an infusion pump arranged inside the liquid storage tank, wherein the liquid storage tank is arranged on a trolley, the trolley comprises a trolley body, roller wheels and a push handle, a support arm is obliquely arranged at the front side of the upper end of the trolley body, one end, far away from the trolley body, of the support arm is rotatably connected with a rotary arm, one end, far away from the support arm, of the rotary arm is fixedly connected with a cross rod, the cross rod is arranged vertical to the rotary arm, both ends of the cross rod are rotatably connected with folding rods, a plurality of spray nozzles are fixedly mounted at the lower end of the cross rod and lower ends of the folding rods, and the rotary arm, the cross rod and the folding rods are all of tubular structures; and liquid spraying pipes are separately arranged in the cross rod and the folding rods, the spray nozzles are connected to the liquid spraying pipes, and the liquid spraying pipes are connected with an output end of the infusion pump through an infusion tube. According to the device, the breadth of spraying of a herbicide can be adjusted, the sprayed herbicide can be prevented from being blown about by wind, and thus, the spraying effect is effectively improved.