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...