Abstract: Objective To explore the relationship among smoking before disease, duration of untreated psychosis (DUP) and the cognitive function in male first-episode schizophrenic patients. Methods A total of eighty-six first episode patients were divided by DUP into short DUP group(n=39) and long DUP group (n=47). Investigate the age at starting smoking, smoking years and smoking amount, the FTND, WCST and P300 were used to evaluate smoking severity and cognitive function and contrasted with 40 health controls. Chi-squared Test, t-test and ANOVA was used to analyze the data. The Pearson correlation analysis was used to analyze the correlation between smoking behavior and cognitive function. Results ①Comparing with controls, the age at smoking in two patient groups were earlier (each P<0.001), smoking amount were higher (each P<0.05), the scores were higher (each P<0.05), and the rate of smoking were higher(each P<0.05). Comparing with short DUP group, smoking amount and scores of FTND were higher (each P<0.05), and the rate of smoking were higher (P<0.05). ②Comparing with controls, there were significantly differences in two patient groups in cognitive function (each P<0.001), and there were significantly difference between two patient groups in cognitive function (each P<0.05) except classification completion number of WCST and latency of P300 (each P>0.05). ③In all patients, the age at start smoking were negatively correlated with the DUP and total number of tests in WCST (r=-0.256, -0.224， each P<0.05), and positively correlated with amplitude of P300 (r=0.274, P=0.011); smoking years was positively correlated with latency of P300 (r=0.225, P=0.037); smoking amount and FTND score were positively correlated with DUP (r=-0.739, 0.720, each P<0.001); FTND score was positively correlated with the Correct Number (r=-0.271, P=0.012). Conclusion Smoking before disease is a risk factor for schizophrenia, which may prolong DUP and eventually lead to cognitive decline.