Degradable backing for emplastrum and preparation method thereof

The preparation method comprises the following steps: 1) preparing a green Chinese onion extract: cutting fresh green Chinese onions into sections, performing vacuum drying, performing extraction by a Soxhlet extraction method for 1-2 hours to obtain an extracting solution, and performing rotary evaporation to remove chloroform to obtain an oily substance which is a fat-soluble component of the green Chinese onion extract; 2) preparing a spinning solution: respectively taking polylactic acid, soya bean lecithin and a green Chinese onion extract, adding a solvent, heating and stirring to obtain the spinning solution; 3) preparing a backing: performing electrostatic spinning under the conditions that the voltage is 10-20kv, the spinning flow rate is 0.2-1.2 mL/h, the spinning distance is 10-19cm, the spinning solution concentration is 10-25%, the spinning film is 45-60 DEG C, heat treatment is performed for 3-4 hours, the spinning diameter is 80-200nm, composite porous nanofibers are prepared, the fibers are wo