Abstract: This paper presents an experimental method to realize the best high-order harmonic generation(HHG) phase matching in the interaction of strong optical field and gas target. By studying the effects of the relative location between gas target source and Gaussian-type driving field focus on the harmonic phase matching, conclusions are obtained that the optimum position of gas target for phase matching is always 3-5 mm behind the focal point of the driving field, with much lower HHG yield before the focus caused by serious harmonic phase mismatch. At the same time, in the optimum relative position, the driving field and the high-order harmonic field have similar spatial distribution characteristics, providing the experimental basis for the commonly used assumptions of Gaussian beam for high-order harmonic field.