A new method was proposed for estimating the influence domain of weight function in moving least square method based on De Giorgi iterative method. The method can estimate the radius of influence of the weight function in local domain, through which the formula of the weight function can be obtained. The algorithm was used for processing the trajectory of a certain aerial bomb. Experimental result showed that: the ballistic trajectory model obtained by the proposed weight function in moving least square method can satisfy the requirement of engineering accuracy, and the smoothness of the fitting curve is improved.