The present invention relates to a high temperature resistant corrosion inhibitor and a preparation method thereof. The preparation method comprises: taking dodecyl dimethyl tertiary amine and polyethylene polyamine, mixing, stirring, and diluting to prepare an agent A, wherein a weight ratio of the dodecyl dimethyl tertiary amine to the polyethylene polyamine is 1:1.5-2.5; taking polyethylene polyamine and morpholine, mixing, stirring, and diluting with water to prepare an agent B, wherein a weight ratio of the polyethylene polyamine to the morpholine is 1.5-2.5:1; taking pyridine and morpholine, mixing, stirring, diluting with water, and uniformly stirring to prepare an agent C, wherein a weight ratio of the pyridine to the morpholine is 1:1.25-1.75; and under a stirring condition, sequentially adding the agent A, the agent B and the agent C to a reaction container, mixing, diluting with water, and uniformly stirring to prepare the high temperature resistant corrosion inhibitor, wherein a weight ratio of the agent A to the agent B to the agent C is 0.75-1.25:1.75-2.15:0.75-1.25.