The invention relates to an application of extracts of fermented red beans and a composition thereof. The preparation method of the extracts of fermented red beans includes steps as follows. Red beans are soaked in water and sterilized under high temperature and high pressure. Bacillus subtilis is added into the red beans to ferment. Finally, the fermented red beans are extracted, which can be used to manufacture compositions for delaying diabetic nephropathy.本發明提供一種紅豆發酵萃取物之用途及基於此用途的組合物。所述紅豆發酵萃取物係以下列步驟所製得:將紅豆浸泡於水中經高溫高壓滅菌,以形成紅豆基質。於紅豆基質中加入枯草桿菌(Bacillus subtilis)進行發酵步驟,以獲得發酵產物。對發酵產物進行萃取步驟,以獲得紅豆發酵萃取物。所述紅豆發酵萃取物可用於製備延緩糖尿病腎病變的組合物。100‧‧‧紅豆發酵萃取物之製備方法110、120、130、140‧‧‧步驟