The invention relates to a soilless substrate for cultivating crops, which efficiently solves the problems of city greening and environmental protection and sterile soil. The technical proposal for solution is as follows: the soilless substrate is prepared by the following components based on weight percentages of 31-63% of plant straw, 9-29% of compound amino acid, 4-12% of powdered charcoal, 10-34% of ground phosphorite and 5-22% of potassium feldspar, the total amount being 100%, during the preparation, after formaldehyde with the mass concentration of 40% is firstly used for dilution 30 times, the plant straw is squirted with water and covered with thin films; exposing of 25-30 hours and air drying are carried out, and plant straw is crashed and poured in a stirrer together with the powdered charcoal; the compound amino acid is then stirred and slowly added at the temperature of 18-30 DEG C to react for 3-5 hours with the plant straw and the powdered charcoal under full stirring; even mixing is carried out, and then ground phosphorite and potassium feldspar are sequentially added; the stirring and reaction last 3-6 hours, and the pH value is 5-6.5 and the soilless substrate isobtained; the invention not only solves the problem of city greening and environmental protection but also can solve the planting problem of organic food of sterile soil and ecological agriculture, having scientific compositions and good use effects and being an innovation in the field of agriculture.