Because active contour models are sensitive to the position of initial contour and concavity target contour can’t converge correctly,an improved algorithm for extracting target contour of infrared images automatically was proposed based on adaptive edge detection and active contour models.Firstly,for reducing sensitivity to the position of initial contour,the adaptive threshold was calculated by OTSU algorithm,and then the first edge would be extracted.Secondly,the first edge was filled horizontally and vertically.For getting the target area,filling images were computed by using AND operation.The second edge which was extracted from the target area was considered as the initial contour of active contour model.This could ensure the effective convergence of boundary concavities.The simulation analysis results show that the infrared target contour could be converged accurately and autonomously by using this method.