Pulsed laser was utilized to treat a commercial purity Zr (CP Zr) sheet coated with Cr by brush plating to achieve Cr alloying on its surface. Microstructural characteristics and hardness of the laser-treated surface were investigated by use of electron channeling contrast imaging, electron backscatter diffraction, energy dispersive spectrometry techniques and microhardness measurement. Results show that after the laser surface alloying (LSA) with Cr, five zones with distinctly different microstructural characteristics are presented from the surface to the matrix: two melted zones (MZs), two solid-state phase transformation zones (SSPTZs) and the unchanged matrix. The MZ-1 and the MZ-2 are featured by equiaxed and columnar structures with internal substructures inside them, respectively. The SSPTZ-1 is fully comprised of martensitic plates transformed from complete �� domains while the SSPTZ-2 contains both martensitic plates and bulk �� grains due to cooling from ��+�� domains. The Cr alloying mainly occurs in the two melted zones (MZ-1 and MZ-2) while essentially not in the SSPTZs. Compared with the initial microstructure, many low angle boundaries appear in untransformed bulk �� grains in the SSPTZ-2, which is related to thermal stresses induced by the laser surface treatment. Hardness measurements show that the LSA with Cr can effectively increase the surface hardness of the CP Zr, with the maximum value (468 HV) to be ���2.4 times that of the matrix. Such hardening could be mainly attributed to solid-solution strengthening of Cr in ��-Zr and significant grain refinement.