A diquat suspension and a preparation method thereof, characterized in that it contains 1-95% of diquat, 1-5% of a thickener, 1-2% of an antifreeze, 1-10% of an emulsifier, and antiseptic Agent 1-2%, water 1-80%. First, pour water, emulsifier, and diquat into a stirring tank according to a certain percentage by weight, stir well, then transfer to a sand mill, cut, sand, and finally add thickener, antifreeze, anti-corrosion After fully stirring, a uniform diquat suspension can be obtained. The diquat suspension of the present invention can be used for pre-emergence treatment, and can also be used for spraying stems and leaves. Suitable for crops such as corn, soybeans, beans, cucumbers, onions, peppers, strawberries, lettuce, eggplant, turnips, and also for lawn and ornamental plants. It is mainly used to control annual grass weeds and some broad-leaved weeds, such as foxtail, crabgrass, brocade, purslane, chickweed, dodder and so on.