The invention provides a rice dry seedling raising substrate, and belongs to the technical field of agriculture. The invention aims at providing a substrate which takes industrial tailings and agricultural residues as the raw materials and is suitable for rice dry seedling raising and a preparation method of the substrate. The substrate is prepared from, by weight, diatomite tailings, bentonite, biochar, vermiculite, organic fertilizer and manure. The rice dry seedling raising substrate is prepared by utilizing the diatomite tailings which are wide in source and low in cost for replacing soil and matching the diatomite tailings with appropriate proportions of other raw materials. The rice dry seedling raising substrate has the advantages that moisture and fertility are preserved, the buffering action is great, air permeability and warming are achieved, the nutrition is balanced, the unit weight of the substrate is small, transport is convenient, the technology is simple, operation is convenient, the labor intensity is low, soil-borne diseases do not exist, the rice seedling quality is good, the seeding raising cost is low, and management is easy. By utilizing the rice dry seedling raising substrate for conducting rice seedling raising, industrial and agricultural waste material resources are fully utilized, existing seedling raising equipment does not needs to be replaced and remolded, acceptability of farmers is rapid, technology transition can be directly achieved, and the rice dry seedling raising substrate is suitable for family seedling raising, industrial seedling raising, mechanical rice transplantation and manual rice transplantation.