The invention discloses an immunity affinity absorber, composed of a solid carrier and a coupled carbostyril drug single-clone antibody. The single-clone antibody is secreted from single-clone hybridomas cell plant A-4-3CGMCC No. 2066. The invention discloses an immunity affinity spectrum post which stuff is immunity affinity absorber, which can at least purify 13 carbostyril drugs, as ciprofloxacin, fleraxacin, or the like. The inventive purifying method combines the spectrum method to high-effect check the content of carbostyril drug, to resolve the defects of single immunity test techniqueas small information amount, low quantitative accuracy, or bad physicochemical selectivity, to show the compensation of immunity technique and general physicochemical technique in analysis mechanism.