Objective To investigate the association between lesion patterns and infarction mechanism in acute infarction patients who had atherosclerotic middle cerebral artery(MCA) stenosis or occlusion. Methods We retrospectively reviewed 138 cases acute infarction in unilateral MCA areas with MCA stem stenosis or occlusion from January 2014 to May 2016, including clinical data and head MR examination(T1WI, T2WI, DWI, MRA). According to distribution of hyperintense on DWI, lesion patterns were divided into perforating artery infarction(PAI), pial infarction(PI), border-zone infarction(BZI). Single infarction had one lesion, multiple infarctions had two or more lesion. According to MRA, the degree of MCA stenosis was divided into moderate, severe, occlusive. Then, we compared the difference between single infarction and multiple infarctions, different stenotic degree. Results 61 cases had single lesion, 77 cases had multiple lesions. Moderate stenosis group had 54 cases, single PAI was the most common infarction type(χ2 =13.197, P<0.001). Severe stenosis group had 58 cases, multiple PI+PAI+BZIwas the most common infarction type(χ2 =5.561, P=0.018). Occlusion group had 26 cases, there was no statistical differernce between single lesion and multiple lesions(χ2 =0.049, P=0.842), but it has many large area infarction cases(χ2 =24.745, P<0.001). Conclusion Different infarction patterns may indicate different mechanism in patients with atherosclerotic middle cerabral artery stenosis or occlusion.