Preparation and application of medicine for treating immunosuppression

The invention discloses a preparation method and application of a medicine for treating immunosuppression. The preparation method comprises the following steps: performing reflux extraction on fine medicinal rhizoma drynariae powder with 8-14 times by weight of ethanol for 1-3 times, wherein each time lasts for 1 hour; filtering, combining filtrate, and performing decompression recycling on ethanol by using a rotary evaporator so as to obtain a concentrated solution; separating by using an AB-8 macroporous resin column, and performing decompression constant-temperature drying at 50-80 DEG C to obtain a half finished product of general flavones of rhizoma drynariae; further separating the half finished product of the general flavones by using a silica gel chromatography column, thereby obtaining rhizoma drynariae general flavones. By adopting naringin as a reference substance, the light absorbancy of a sample is tested at 283nm by using an ultraviolet spectrophotometric method, and tests show that the content