Abstract: Using in situ polymerization process, polymethylmethacrylate (PMMA) binding agent was obtained on NdFeB magnetic powders , and PMMA/NdFeB bonded magnets were prepared. Infrared spectroscopy was employed to analyze the polymerization products. Structure, hardness, mechanical properties and magnetic property of the bonded magnets were analyzed by means of scanning electron microscopy, Shore durometer, tensile testing machine and automatic recording fluxmeter, respectively. Effect of the magnetic powder content on mechanical and magnetic properties of bonded magnets was studied. The results show that content of magnetic powders had no effect on the structure of polymerization products. Grafting rate of PMMA on the surface of NdFeB magnetic powders gradually decreased with increasing the magnetic powder content from 80% to 92%. While the hardness, density, coercive force, remanent magnetization and maximum energy product of bonded magnets increased monotonously. The tensile strength of the bonded magnets increased first then decreased, showing a maximum at the powder content of 88%.