The invention relates to a processing system of a CT image, which comprises a CT image acquiring module, an interesting region estimating module, a characteristic extracting module, an abnormal signal identifying module and a displaying module. The CT image acquiring module is used for acquiring a head CT image subjected to brain tissue segmentation; the interesting region estimating module is used for estimating an interesting region of subarachnoid space to the head CT image; the characteristic extracting module is used for extracting the characteristic to the head CT image subjected to the estimation of the interesting region to acquire a characteristic value; the abnormal signal identifying module is used for identifying whether an abnormal signal is included in the interesting region according to the characteristic value by using a method of mode identification; and the displaying module is used for displaying the identified result and the interesting region in which the abnormal signal exists. The invention also relates to a processing method of the CT image. The invention can display a position in which the abnormal signal exists, which is referred by medical staffs, so as to reduce misdiagnosis/missed diagnosis rate of the subarachnoid space hemorrhage.