The invention belongs to the technical field of rubber tree seedling culture and particularly discloses a soil-free organic waste substrate suitable for rubber tree seedling culture. The substrate is composed of cassava peels, bagasse ash and peanut shells; the cassava peels and the peanut shells are subjected to stack retting composting treatment. According to the substrate suitable for rubber tree seedling culture, organic materials such as common agricultural and forestry residues easy to obtain in rubber planting areas are utilized, in addition, components and matching of the substrate are optimized, the obtained substrate achieves good physicochemical properties, the quality of rubber seedlings can be effectively improved, the production period is shortened, and the production cost is reduced.