The GaN epitaxial wafers with a p-GaN surface are irradiated with an excimer laser at different energy densities and pulse numbers. The laser irradiation induced changes in optical and electrical properties of GaN epitaxial wafers are examined using photoluminescence, cathode luminescence, X-ray photoelectron spectroscopy, Hall, I-V characterization. Experimental results show that under an appropriate laser irradiating condition and annealing treatment in N2, the luminescent and electrical properties of the samples are improved to different degrees. The irradiated and annealed samples are transformed into light emitting diode (LED) device with semiconductor packing process, and the relationship between the luminescent properties of LED and the laser energy density or annealing atmosphere are investigated. After laser irradiaiton and annealing treatment, the light output power of GaN- based LED increases at least about 37% compared with non- irradiated samples, which shows that the improvement of the electrical properties of GaN epitaxial materials plays important role in enhancing the luminescent properties of the LED device.