The invention belongs to the field of high-polymer materials, and discloses a preparing method of a full-cell polymer foaming material and the foaming material prepared through the method. The methodincludes the following steps of firstly, selecting a non-water-soluble thermoplastic polymer or a mixture of the non-water-soluble thermoplastic polymer and a water-soluble thermoplastic polymer to prepare a blank; secondly, coating the surface of the blank with a water solution of the water-soluble thermoplastic polymer to prepare a protection blank; thirdly, conducting supercritical fluid foaming on the protection blank to prepare a foaming blank; fourthly, conducting leaching and drying on the foaming blank to prepare the finished product. The size of cells in the surface of the prepared foaming material is 5-20 micron, and the cell density is not lower than 1.0*10<7> cell/cm<3>. Compared with the prior art, the surface porosity is high, the internal cell structure is not broken, and the material is free of pollution, environmentally friendly and low in production cost.