Objective Vascular dementia and alzheimer's disease brain MRI contrast analysis. Methods This article selects the hospital in January, 2015 to May 2014 treated 35 cases of vascular dementia and alzheimer's patients, for all the patients with brain magnetic resonance imaging (MRI) scan in the diagnosis of, further the scan in the diagnosis of MRI image to analyze, compare two groups of patients with hippocampal volume measurement size and grade of LA situation and imaging results. Results The vascular dementia group of patients with hippocampal volume average (4.80+0.27) cubic centimeter, alzheimer's disease patients hippocampal volume averaged cubic centimeter (4.44+0.24), the results of two groups exist significant difference(P<0.05), with statistical significance. There are the results of two groups of LA is more significant difference (P<0.05), with statistical significance. Conclusion Vascular dementia and alzheimer's patients, there are many differences between MRI images of the brain needs to be combined with clinical treatment and diagnosis process to effectively identify and diagnose them.