Objective To explore the correlation between lipopolysaccharide( LPS) in blood endotoxin and cerebrospinal fluid( CSF) and schizophrenia. Methods The blood and cerebrospinal fluid test results of 6 schizophrenic patients with positive blood LPS test were retrospectively analyzed. Results The LPS in blood was 0.063-0.669 EU/ml, and the LPS in CSF was 0-1.018 EU/ml. There were 4 positive cases. There were 3 cases of White Blood Count( WBC) higher than 10×109/L,and 1 patient of neutrophile granulocyte( NE%) more than 70%. The antistreptolysin O( ASO) were from 25 to 606 IU/ml, moreover 1 patient' ASO were higher than 116 IU/ml. Conclusions The LPS in CSF are positive in some schizophrenic patients who were positive hematal LPS. Therefore we assume that infection may be related to schizophrenia, and the brain external infection may be the pathogenesis of schizophrenia.