The invention provides a melt spinning method of superfine denier spandex fibers through the reaction in a single static reaction kettle. The method is characterized by comprising the following steps: taking raw material components; feeding under a negative pressure; applying the nitrogen pressure of 0.8MPa; carrying out a high-temperature natural reaction in the static reaction kettle; conveyingthe materials to a double screw extruder; filtering by a melt filter; cooling the ejected silk via an air channel; applying oil by an oiling device; drawing guide silk by a two-pass silk guide roller; and curing in a drying room, detecting and packing. The obtained superfine denier spandex fibers have the advantages of small bending rigidity and particularly soft hand feeling; meanwhile the surface area of the fibers is very large, thus the coverage, bulkiness and thermal insulation property of fabrics are obviously improved and the extremely strong cleaning function is achieved; the superfine fibers can be made into super-high density fabrics, and the clearances among the fibers are remained between droplet diameter and steam microdrop diameter, thus having waterproof and air permeability effects; and when the fibers are processed into wettable towel fabrics, the moisture can be quickly absorbed from washed hair so as to quickly dry hair by utilizing the towel with high water absorbability. The obtained superfine denier spandex fibers can be applied to various fields.