The present invention describes a method of inhibiting inflammatory response by using a lipopolysaccharide of Parabacteroides goldsteinii. The lipopolysaccharide of Parabacteroides goldsteinii can effectively inhibit the immune responses caused by pathogenic lipopolysaccharides in peripheral blood mononuclear cells, macrophages, and/or B cells, and then can be effectively used to inhibit the inflammatory responses and the preparation of the related compositions.