The development of a robust and efficient stationary phase for chromatographic biopharmaceutical purification is of prime importance but remains challenging. Herein, we have developed a series of protein A-mesoporous silica composites for the first time by covalently coupling protein A with the tagged carbonyl imidazole moieties in the column, which constitutes a facile and efficient route for the preparation of protein A immunoaffinity materials. The resultant composites are employed as the stationary phase for chromatographic purification of immunoglobulin G (IgG). The effect of silica's pore size and coupled protein A on the antibody purification is systematically investigated. When the pore size of silica increased from 100 to 1000 Å, the amount of coupled protein A decreased, and the surface coverage on the silica significantly improved, accompanied by an increase in the amount of purified rabbit IgG. With an increasing coupled protein A, the surface coverage increased at first and decreased subsequently, which shows a similar trend to the amount of purified IgG and specific activity. When practically implemented for purifying several immunoglobulins that are central for commercial ELISA Kits, the protein A-mesoporous silica composite exhibited superior performance compared to the GE-Mabselcetxtra rProtein A column, particularly in the purification of immunoglobulin M (IgM), which cannot be realized by the GE-Mabselcetxtra rProtein A column. This study sheds new light on the rational development of protein-affinity chromatography for biopharmaceutical purification.