The invention provides a plasma filtering device and a plasma filtering method for treating acute cerebral infarction. The device comprises an outer shell and a filter element, wherein the outer shellcomprises an upper shell and a lower shell which is connected to the upper shell; an accommodating space is formed between the upper shell and the lower shell; the filter element is arranged in the accommodating space; the filter element comprises first filtering membranes, a second filtering membrane and a third filtering membrane; along the flowing direction of plasma, the filter element is constituted in accordance with an arrangement mode of the first filtering membrane, the second filtering membrane, the first filtering membrane, the first filtering membrane and the third filtering membrane, wherein the first filtering membrane is a DELP membrane having a liposome and fibrinogen original affinity adsorption function; the second filtering membrane is an EKSP deep filtering membrane which is capable of adsorbing inflammatory factors and free radicals; and the third filtering membrane is a 0.2mm membrane for filtering out various granular materials with granule size greater than 0.2mm. The plasma filtering device has the advantage that plasma of a patient with the acute cerebral infarction can be filtered.