The invention provides a low-expansion coefficient polyvinyl chloride alloy material and a manufacturing method thereof. The ingredients of raw materials of the alloy material comprise a polyvinyl chloride substrate, a heat-resistant modifier, a heat stabilizer, a lubricator, a filler and a processing agent, and the alloy material is manufactured by a melt blending technique. The processing agent and the filler in the ingredients of the raw materials of the invention are the processing agent that is subjected to modification by a new method and the filler that is subjected to organic treatment, and by means of a mechanochemical reaction, self-plastification, toughening and reinforcement of the PVC can be combined organically to improve compatibility and dispersity of the polyvinyl chloride, the filler and heat-resistant resin, thus settling the problem about the contraction between the improvement of heat expansion performance and heat resistance of the PVC, and processing performance, strength and toughness of the PVC; the polyvinyl chloride engineering plastic with low expansion coefficient, high heat resistance, high strength, high toughness, excellent aging resistance and outstanding processing performance is manufactured; the invention has extensive industrial market prospect and the manufacturing method thereof is simple in technology, convenient in operation and control, stable in quality and high in production efficiency.