Abstract: his paper presents a new algorithm for determining parallax of aerial images with analyzing the property of aerial images and corresponding edge-images. Firstly the authors get the data of edges and grads in a pair of aerial stereo images using Canny operator, then produce the histograms of grads of edges in horizontal direction and in vertical direction respectively. After calculating the correlation coefficients of the two histograms of grads of edges with different relative migration, the migration is the parallax in horizontal direction and in vertical direction where the coefficient is the maximum. The experiment results show that the algorithm is reliable and efficient.