The invention discloses a preparation method of microfiber leather. The production line of the preparation method comprises the following steps: production of a high-density spunlaced nonwoven fabricfrom sea island short fibers, ironing shrinkage, wet impregnation in PU resin, toluene reduction extraction, drying tentering, oiling softening, puffing , dry PU lamination, and functional treatment for producing the microfiber leather. The preparation method has the advantages of simple treatment process and environmentally-friendly production process, the microfiber leather contains no chromiumor other harmful substances, the raw material is a petroleum product, is environmentally friendly and nontoxic, and can be recycled, and the microfiber leather produced by the preparation method has the advantages of uniform thickness, excellent moisture absorption property, excellent air permeability, excellent mold resistance, excellent alkali resistance, excellent aging resistance and excellentwater repellency.