Al-doped ZnO (AZO) nanoparticles were synthesized by using homogeneous precipitation method from Zn(AC)2•2H2O and Al(NO3)3•9H2O. X-ray diffraction (XRD) showed that the AZO nanoparticles were well assigned to hexagonal wurtzite structure, and that the Al3+ did enter the ZnO crystal lattice to substitute the position of Zn2+. Results from scanning electron microscope (SEM) showed that with increasing Al content, the the size of ZAO particles decreased. When Al content was 5 mol%, gives a more homogeneous and finer microstructure. At last, study the electromagnetic performance of AZO particles with different doping concentration of Al3+.