ZnO:Cr layer was prepared by Cr ion implantation into ZnO bulk crystals. The structural, optical, and magnetic properties of the ZnO:Cr layer were studied with X-ray diffraction, photoluminescence, and superconductor quantum interferometer, respectively. The ZnO:Cr layer implanted Cr with a dose of 5 10 16 cm 2 remained wurtzite structure and exhibited near-band-edge photoluminescence at 3.365 eV with full-width at half-maximum of 8.4 meV at 10 K. The magnetic measurement showed that the ferromagnetism changed at room temperature by different Cr concentration. For samples implanted to high doses, remanent magnetization reached 1.805 10 -4 emu/g and coercive field was 244.5 Oe. Hall effect measurement showed a decrease of the resistivity from 251.7 cmto 28.6 cmafter annealing at 800 ℃. The magnetism is interpreted by bound magnetic polarons, which were taken into account of the process that electrons were locally trapped by oxygen vacancies and occupied the orbitals that overlapped with d shell of neighboring Cr ions. ZnO: Cr 层 was prepared by Cr ion implantation into ZnO bulk crystals. The structural, optical, and magnetic properties of the ZnO: Cr layer were studied with X-ray diffraction, photoluminescence, and superconductor quantum interferometer, respectively. layer implanted Cr with a dose of 5 10 16 cm 2 remained wurtzite structure andeded near-band-edge photoluminescence at 3.365 eV with full-width at half-maximum of 8.4 meV at 10 K. The magnetic measurement showed that the ferromagnetism changed at room temperature by different Cr concentration. For samples implanted to high doses, remanent magnetization reached 1.805 10 -4 emu / g and coercive field was 244.5 Oe. Hall effect measurement showed a decrease of the resistivity from 251.7 cmto 28.6 cmafter annealing at 800 ° C. The magnetism is interpreted by bound magnetic polarons, which were taken into account of the process that these metals were locally trapped by oxygen vacancies and occupied the orbitals that overlapped wi th d shell of neighboring Cr ions.