The invention discloses a liquid fertilizer degradable water ball for planting corn in farmland in an arid area and a use method thereof. The degradable water ball is mainly composed of urea, ammoniumnitrate, calcium superphosphate and potassium sulfate, a fungicide and a surfactant are added in the mixture and are mainly used for improving the solubility of a tackifier, and speed control over moisture release after plastic degradation is realized; all components are fully mixed and sealed in a degradable plastic ball, and then the liquid fertilizer degradable water ball is obtained. The liquid fertilizer degradable water ball is planted together with corn, and the moisture requirement and the sylvite and nitrogen requirement during corn growth are met; the tackifier and the surfactant for improving the solubility of the tackifier are added to realize slow release of the fertilizer; the consumption of chemical fertilizer in corn planting is effectively reduced, mixture and nutrients required for corn growth are provided in the critical period of corn growth, the evaporation of moisture is prevented, moisture is saved, directed fertilization is realized, the planting cost is reduced, and the influence on soil is reduced.