The invention relates to a preparation method for superfine-fiber elastic base cloth. The preparation method comprises the following steps of: (1) dipping sea-island fiber non-woven cloth in DMF (dimethyl formamide) solution of polyurethane added with carbonate and organic acid; (2) soaking a semi-finished product obtained in the step (1) in the DMF solution, carrying out solidification and foaming treatment, and preparing the polyurethane component into elastomers containing foam holes; (3) washing; (4) using an organic solvent to dissolve off 'sea' parts in the sea-island fibers; and (5) drying and setting. According to the preparation method, in the solidification process of the polyurethane, a solvent DMF in polyurethane slurry generates exchange with water in solidified liquid, and is moved into the solidified liquid so as to generate physical foaming micropores; and simultaneously, when the mixture of the carbonate and the organic acid meets water, the organic acid is dissociated to generate H+ ions which react with the carbonate to generate CO2 gas, so that resin generates chemical foaming micropores, the microporous structure of a polyurethane sponge body can be adjusted, the foam holes are improved and added and the polyurethane sponge body is full and elastic.