Abstract: Passive location of non-cooperative illuminators is a pivotal problem.The algorithm of inverse diffraction parabolic equation with good applicability and stability is widely used for the application of passive location in complex environment.Based on the location method in the symmetrical atmosphere,the location schemes of single and couple illuminators are analyzed in the situation of standard atmosphere and terrain defilade.The methods of the effective data selection and error ellipse protraction are proposed,and the relationship between data number,refraction index,terrain height and location error is investigated in this paper.The suggestions on the parameters selection are presented, which improve the location accuracy and extend the application area of this algorithm.