The invention relates to the technical field of medical auxiliary recognition and relates to a focus recognition method for ischemic stroke magnetic resonance images. The method comprises an image input step, a DWI image processing step, an ASL image processing step, an infusion calculation step, a low perfusion calculation step, a DWI three-dimensional reconstruction step, an ASL three-dimensional reconstruction step, and an ischemia semi-dark zone identification step and the like. In the DWI image processing step and the ASL image processing step, a morphological method is adopted to enhance the characteristics of the image. Focus segmentation and direct volume calculation are realized based on a segmentation method of an adaptive threshold value. Ischemia semi-dark band recognition is realized through an image registration algorithm, and then a Mismatch value is calculated. The cerebral arterial thrombosis lesion position can be accurately recognized, a specific lesion volume value is provided, three-dimensional visual data display is provided, an accurate reference basis is provided for diagnosis and treatment of doctors, and clinical decision making of the doctors is assisted.