What is the principle of polystyrene pore-forming agent? Compared with ordinary polymer microspheres, polymer porous microspheres have the advantages of porous structure, high crosslinking degree and stable mechanical properties. Porous structure leads to its large specific surface area and much smaller osmotic pressure, while high crosslinking degree can make it have stable mechanical properties, so it is widely used in chromatography and other aspects. As a key component of liquid chromatography, the performance of chromatographic column depends largely on the performance of chromatographic column packing. More and more researchers began to pay attention to the modification of porous microspheres to improve their chromatographic separation performance. In this paper, polymer porous microspheres synthesized by two-step swelling method have the advantage of monodispersity. In order to realize accurate and controllable synthesis of porous microspheres, the factors affecting polymer porous microspheres were investigated and improved, and their chromatographic properties were studied. The specific work is as follows: 1. Porous polystyrene microspheres with good monodispersity were successfully synthesized by two-step seed swelling polymerization, and the particle size of the microspheres was 5 μ m. In order to realize the precise and controllable synthesis of porous polymer microspheres, the effects of pore-forming agent ratio, swelling temperature and crosslinking agent types on the surface morphology of porous polymer microspheres were investigated. When the ratio of dibutyl phthalate to toluene is 1:3, the specific surface area of polystyrene porous microspheres is the largest, and the surface is the roughest when the swelling temperature is 25℃. Porous microspheres with ethylene glycol dimethacrylate (EDMA) as crosslinking agent have loose structure. The specific surface areas of various microspheres were compared, and the results showed that the specific surface area of P(S-DVB)-4 was the largest, which was 562 m2/g. 2. Polymer porous microspheres were modified with diazo resin, and the modified microspheres were used as chromatographic column packing for many times. Based on the reaction principle of photocrosslinking, the functional modification of polymer microspheres was realized with water-soluble photosensitive polymer diazo resin. Firstly, the microspheres were sulfonated, then grafted with diazo resin and sulfonic acid groups, and finally the electrostatic interaction was transformed into valence interaction by ultraviolet lamp. The polarity of the stationary phase is improved, which not only retains and enhances the performance of nonpolar substances, but also realizes the separation performance of polar substances. In this paper, the synthesis of porous polystyrene microspheres has investigated the effects of various factors on the surface morphology of polymer porous microspheres, which is of certain significance to realize the controllable pore size distribution and specific surface area. The subsequent modification of porous microspheres combines many advantages of physical adsorption and chemical bonding. Photocrosslinking can realize simple and rapid functional modification of polymer microspheres, which is an efficient, stable and environment-friendly modification method. Both nonpolar and polar substances have achieved good separation performance.