The invention relates to the technical field of cottonrose hibiscus pot culture, and discloses a cottonrose hibiscus pot culture substrate. The cottonrose hibiscus pot culture substrate is prepared from, by volume percent, 10-73% of garden soil, 10-40% of coconut coir, 10-25% of vermicompost, 5-15% of vermiculite or perlite, 0.5-2% of biochar, 1-5% of potassium humate and 0.5-3% of phlogopite. A cottonrose hibiscus pot culture method includes the following steps of 1, preparation of the pot culture substrate; 2, treatment of the pot culture substrate; 3, planting. The cottonrose hibiscus pot culture substrate can keep a loose state for a long time, has good air permeability and strong water retention performance, and keeps a certain constant temperature state, so that the environment conducive to the growth characteristics of cottonrose hibiscus is achieved, and by adopting the cottonrose hibiscus pot culture substrate and the pot culture method, the cottonrose hibiscus can grow well under the condition of the pot culture substrate.