Abstract: Firstly, polysulfone(PSF) was chloromethylated, obtaining chloromethylated polysulfone (CMPSF), and then the CMPSF membrane was prepared by solution casting method. Subsequently, the CMPSF membrane was made to react with ethanediamine (EDA) as agent, resulting in the aminated membrane, namely AMPSF membrane, on which EDA was bonded and amino groups were introduced onto the surface of the membrane. On this basis, a surface initiating system of amino group peroxysulphate was constituted, and it initiated methacrylic acid to produce graft polymerazation on the membrane, obtaining the grafted membrane PSF-g-PMAA. The effects of main factors on the graft polymerization of MAA were investigated, and the reaction conditions were optimized. The grafted membrane of PSF-g-PMAA was characterized by Fourier Transforan Infrared Spectroscopy (FT-IR) and Optical Microscope (OM) as well as weighing method. Finally, the adsorption character of the grafted membrane of PSF-g-PMAA for two alkaloids, oxymatrine and cytisine, was examined. Results show that by using surface initiating system of amino group peroxysulphate, the graft polymerization of MAA on the surface of the aminated membrane, AMPSF membrane, can be smoothly carried out, and the grafting degree of PMAA increases with the content of amino group on the basement membrane AMPSF. The suitable temperature for the graft polymerization of MAA is 50 ℃, and the appropriate dosage of the initiator peroxysulphate in the solution is 1.0% of the monomer mass. Under the optimum conditions, the grafted membrane PSF-g-PMAA with a PMAA grafting degree of 4.62 mg/cm2 can be gained. The functional grafted membrane PSF-g-PMAA can produce strong adsorption action for alkaloid compounds. By right of the synergism of electrostatic interaction and hydrogen bonding, the adsorption capacities of graft membrane on PSF-g-PMAA can reach 277 μg/cm2 for oxymatrine and 331 μg/cm2 for cytisine, respectively, in neutral solution.