The invention discloses a foliar preparation for improving crop resistance and a preparation method thereof, wherein the foliar preparation comprises an amino acid fermentation waste liquid, potassiumhumate, alginic acid, a macroelement fertilizer, a medium-trace element fertilizer, a surfactant, a plant growth regulator, a pH regulator and a suspension thickening agent. The foliar preparation ofthe invention adopts the amino acid fermentation waste liquid as the main organic component to realize waste liquid utilization, so that resources are saved, and the foliar preparation is environmentally friendly and safe. In addition, the amino acid fermentation waste liquid is rich in small molecular water-soluble organic matter, can chelate trace elements, can directly provide organic nutrition to plants, and promote nutrient absorption, thereby ensuring the accumulation of carbohydrates and nutrient absorption in plants in continuous rain and haze weather, maintaining healthy growth, andeffectively preventing occurrence of wilting, yellow leaves and the like of the plants, and therefore the cold resistance and disease resistance of crops are improved, and increase of the crop yield is facilitated.