Cognitive impairment is the core symptom of schizophrenia. Atypical antipsychotics treatment can easily induce metabolic syndrome in patients， and metabolic syndrome can further aggravate their cognitive impairment. The internal mechanisms causing this series of clinical symptoms mainly include the following： brain-derived neurotrophic factor mechanism， insulin resistance mechanism， intestinal flora mechanism， immune inflammation mechanism and micro vasculopathy mechanism. Based on the complicated relationship among atypical antipsychotics， metabolic syndrome and cognitive impairment， this article reviews the correlation among them and the related biological mechanisms that have been discovered.