In order to realize the third harmonic propagating at high-power and irradiating target, a method based on the combination of wedge window and focus lens has been proposed to serve the important function of angularly dispersing the unconverted the fundamental and second harmonic away from the third harmonic target in high power laser facility. Based on the multifunctional and high-power laser system of “Shenguang-Ⅱ” facility, the wedge window is designed. And resulted from the wedge window, the B-integral and the space error between the second harmonic and third harmonic are analyzed. In experiment, the third harmonic propagating at high-power has been improved from 0.7～1 J/cm2 to 2.8 J/cm2, and the space is up to 2.85 mm at the third harmonic target. The method can be used to achieve the third harmonic splitter in high power laser facility.