The invention provides a high-temperature-resistant starch-based scale inhibitor, and a preparation method and application thereof. The high-temperature-resistant starch-based scale inhibitor comprises the following raw materials in percentage by weight: 6-12% of starch base, 12.6-14.7% of acrylic acid, 3.6-9.6% of 2-acrylamido-2-methylpropanesulfonate, 0.4-0.8% of composite initiator and the balance of water. The preparation method of the high-temperature-resistant starch-based scale inhibitor comprises the following steps: under the action of the composite initiator, stirring the starch base, the acrylic acid and the 2-acrylamido-2-methylpropanesulfonate at 50-60 DEG C, and performing polymerization reaction for 4-6 hours, thus preparing the high-temperature-resistant starch-based scale inhibitor. The high-temperature-resistant starch-based scale inhibitor can be used for scale inhibition of oilfield water, industrial water and domestic water. The high-temperature-resistant starch-based scale inhibitor has the characteristics of high temperature resistance, high efficiency, no toxicity, no secondary pollution and the like.