The invention discloses a preparation method of unsalted dried sea cucumbers. The preparation method comprises the following steps of: pre-treating sea cucumbers, removing water, pickling, perforating, desalting, shaping, drying at a first stage, drying at a second stage, drying at a third stage, performing microwave vacuum drying, and packaging. Because the sea cucumbers are perforated, the sea cucumbers can be desalted and dried more easily and can be rehydrated more easily during eating. The staged drying can avoid the defect that water is difficult to discharge at the later stage because the water is excessively lost at the earlier stage; and during the microwave vacuum drying, concentration differences are used for driving water to migrate and diffuse, and pressure and temperature differences are used for driving steam and liquid to be directly discharged, so that the drying time is short, and the original flavor and nutrient ingredients of the product are kept.