The present invention discloses an application of β-glucan for preparing drugs of inhibiting abnormal increase of immunoglobulin A (IgA). The β-glucan is extracted from Saccharomyces Cerevisiae, and the effective dose of the β-glucan is 300-450 mg/70 kg of body weights/per day, preferably, 350-400 mg/70 kg of body weights/per day.本發明係揭露一種β-葡聚糖(β-glucan)的用途,其係用於製備抑制免疫球蛋白A不正常上升之藥物。其中β-葡聚糖可從啤酒酵母菌萃取而得,且β-葡聚糖的有效劑量為每日每70公斤體重300毫克至450毫克,較佳為每日每70公斤體重350至400毫克。