The invention provides a substrate and a method for cultivating color peppers in a solar greenhouse in saline-alkali soil, and belongs to the technical field of vegetable cultivation of salt-alkali soil. The substrate disclosed by the invention comprises a filling substrate and a cultivation substrate, and the substrate has strong water and fertilizer holding capacity, good air permeability, goodheat storage property and strong heat exchange capacity with soil. The method provided by the invention comprises the following main steps: arranging a cultivation tank in the solar greenhouse, and sequentially laying an isolation film, a filling substrate, an insect-proof net and a cultivation substrate in the cultivation tank; applying an EM bacterial agent and an amino acid liquid fertilizer tothe substrate of the cultivation tank; planting the color peppers, and applying an attractant after planting; harvesting the color peppers, pulling seedlings, applying allyl isothiocyanate, and closing the greenhouse. The method provided by the invention can slow down salinization of the substrate, control the occurrence of soil-borne diseases, reduce the use of chemical pesticides and improve the yield of the color peppers.