Abstract: In order to address the problem of detecting and locating the anterior cruciate ligament of human's knee in medical image and promote the study of its reconstruction operation, this paper proposes a hierarchical detection based method to locate the anterior cruciate ligament.The location task is performed in the global and the local detections successively.The features are selected according to the type of image samples, and the corresponding global and local detectors are built based on the random forests respectively to first find the entire region of the anterior cruciate ligament and then recognize its definite area.Experimental results based on the real MRI images validate the effectiveness and accuracy of our method.