Objective To investigate the relationship between plasma nitric oxide （NO） concentration， nitric oxide synthase （NOS） activity and cognitive function and clinical symptoms in male patients with chronic schizophrenia. Methods A total of 96 male patients with chronic schizophrenic were selected as the patients group in Lianyungang psychiatric hospitals （The Fourth People's Hospital of Lianyungang， Rehabilitation Hospital of Ganyun District， Psychiatric Hospital of Donghai， Psychiatric Hospital of Guanyun） from January to October 2020. Another 88 healthy male aged from 18 to 60 were recruited from January to October 2020 in Lianyungang as the control group. The plasma nitric oxide （NO） concentration and the activities of primary nitric oxide synthase （cNOS） and inducible nitric oxide synthase （iNOS） were detected. The cognitive function of all the research objects was measured by the Repeatable Battery for the Assessment of Neuropsychological Status （RBANS）. The Positive and Negative Syndrome Scale （PANSS） was used to evaluate the mental symptoms of the patients. Results The level of NO in the patient group was higher than that in the normal group ［（53.1±16.7） μmol/L vs （48.0±16.8） μmol/L］， and the difference was statistically significant （P=0.017）. The activity of cNOS in the patient group was lower than that in the normal group ［（1.3±0.5） U/ml vs （1.6±0.5） U/ml］， with statistical significance （P＜ 0.001）. There was no significant difference in the activity of iNOS between the two groups ［（1.7±0.5） U/ml vs （1.6±0.7） U/ml， P=0.160］. The total score of RBANS and five subscales in the patient group were significantly lower than those in the control group （all P ＜ 0.01）. In the patient group， NO concentration was positively correlated with body mass index （BMI） （r=0.353， P ＜ 0.001）， course of disease （r=0.257， P=0.012）， PANSS positive symptom score （r=0.331， P=0.001）， PANSS general pathological score （r=0.204， P=0.047）， and negatively correlated with age of onset （r=-0.320， P=0.001）， the score of speech function of RBANS （r=-0.281， P=0.005）. There was no significant correlation between the activity of cNOS and iNOS and clinical features， PANSS score and RBANS score in the patient group （all P ＞ 0.05）. There was significant difference in speech function ［（76.1±11.3） vs （68.5±14.3）， P ＜ 0.05］ between low NO concentration group ［（39.6±10.6）μmol/L］ and high NO concentration group ［（66.2±9.5）μmol/L］. Conclusions The cognitive function of chronic male schizophrenia is significantly impaired. The activities of plasma NO and its synthase are abnormal， and there is a correlation between plasma NO and the clinical characteristics of patients， suggesting that the mechanism of oxidative stress may play a role in the pathophysiological mechanism of schizophrenia.