An asplenium nidus extract is used for preparing medicines or health food for improving prostate diseases, and contains pyropheophorbide acid-alpha methyl ester, phaeophorbide-alpha methyl ester, 1-linoleic acid-3-linoleic acid-glyceride, 1-linoleic acid-2,3-dipalmitic acid-glyceride, and 1,3-dipalmitic acid-glyceride. The asplenium nidus extract is prepared from a method including: a step of solvent extraction by using an extraction solvent to perform extraction processing on an asplenium nidus sample, so that the weight volume ratio (w/v, g/ml) between the asplenium nidus sample and the extraction solvent is 50 to 60 mg/ml, and an extract is obtained and a step of column chromatography by using water and ethyl alcohol as mobile phases and performing the chromatography separation processing of the extract to obtain a plurality of differentiation objects which are numbered as segment a to segment I according to the chronological order of elution, and selecting the segments b, c and d or compositions thereof for vacuum concentration and freeze drying, and then the asplenium nidus extract is obtained.
