In this paper, we focus on studying the small sample passive location probability method to the moving target. Based on the known conditions about the sequence of latitude and longitude change with time, the sequence of flight altitude changes with time, the information of angle of arrival (azimuth angle/angle of pitch), we propose a novel passive location algorithm by virtue of the equiprobability curve theory. And we present an algorithm of error estimation. However, the traditional flat ground passive location algorithms do not consider the effect of the curvature of the earth's surface. In this paper, we consider the effect of the curvature of the earth's surface to the passive location. Moreover, theoretical analysis shows that the traditional location method is the first order approximation of our algorithm. Numerical experiments confirm that our algorithm has higher accuracy than the traditional location method.