Optimum deployment in double-plane passive location system is concerned. Giving the distance of target and my plane and in the sense of the minimum Circular Error Probability (CEP), some significant conclusions are given. The research indicates that the optimum sensors deployment is dependent on the distance of two planes and the cut angle of two planes and target. The optimum deployment should satisfy that the two planes distance D is 1~1.2 times of the distance of my plane and target D1, and the formed cut angle β is in 90°-θ1/2<β<90°. These conclusions can be applied for reference in optimal deployment of double passive sensors to obtain high location accuracy.