The invention discloses a tobacco substrate suitable for a heat-not-burn effect and a preparation method thereof. The method comprises the following steps of 1, obtaining tobacco powder with particle size distribution of 60-200 mesh after tobacco raw materials are ground into powder and sieved, and obtaining wood pulp fiber powder with size distribution of 60-200 mesh after wood pulp fibers are ground into powder and sieved; 2, mixing the tobacco powder, the wood pulp fiber powder, adhesives, filler, moisturizing agents, flavors, fragrances and tobacco extracts according to a ratio to obtain mixed slurry, then adding water in the mixed slurry for stirring, and conducting uniform mixing to obtain loose granular slurry; 3, pressing the granular slurry into sheets, and conducting drying after sheet pressing to obtain the sheet-shaped heat-not-burn tobacco substrate. In the preparation process of the substrate, the step is taken into consideration that the tobacco raw materials are ground into powder at first, and the structures of the fibers are destroyed, so that the specific surface area of the raw materials is increased; meanwhile, the strength problem in the molding process is taken into consideration, partial long wood pulp fibers are adopted to be ground into powder to improve the strength of the substrate, and the powder is mixed with the tobacco extracts more uniformly during preparation.