MRI of the brain in developmental delay may show reduced brain volume, brain tissue defects, abnormal myelination of the brain white matter, widening of the extracerebral space, enlarged ventricles, abnormal development of the cerebral cortex, and hypoplasia of the corpus callosum, but it should be diagnosed in conjunction with other tests as well. MRI checks out the brain development, which is very helpful in the diagnosis of brain developmental delay. People with brain developmental delay show daily manifestations such as dull expression, speech communication disorders, abnormal movements, emotional disorders, mental retardation, and slow reaction time. However, some patients with brain developmental delay do not have obvious manifestations on imaging, which cannot be effectively diagnosed by MRI, and need to be accompanied by EEG, CT and other corresponding examinations of the brain, therefore, the diagnosis of brain underdevelopment cannot be confirmed only from the manifestations of MRI. Brain developmental delay should be treated as early as possible, but the treatment period will usually be longer, and more care should be given to the patient in daily life to avoid other damages to the body.