Objective To explore the sleep characteristics in first-episode schizophrenics and the effects of olanzapine on body weight and sleep-breathing disorder.Methods 36 first-episode schizophrenics (patient group) and 33 normal controls (control group) were tested with polysomnography(PSG),and compared the difference of PSG,sleep-breathing index and body mass index(BMI) before and after treatment in patient group.Results Before treatment,compared with control group,the patient group had significantly prolonged sleep latency((83.64± 10.62) min vs (29.41 ± 10.05) min),shortened total sleep time ((286.43 ± 17.04) min vs (343.66 ± 16.38)min),decreased sleep efficiency((65.73 ±11.47) vs (86.13 ± 8.15)),increased awake time and arousal number((65.70 ± 10.33) min vs (25.93 ± 9.60) min ; (38.26 ± 6.88) vs (14.40 ± 2.72)) in sleep continuity ; and increased N1 stage ((87.43 ± 11.35) min vs (36.55 ± 6.40) min),decreased N2,N3 stage ((100.53 ± 10.42)minvs (143.35±13.52)min;(49.83±7.51)minvs (87.52±9.74)min) in sleep structure (P ＜ 0.05).After treatment,sleep continuity and sleep structure in patient group were improved,compared with control group,only BMI,arousal index and hypopnea index had statistic difference (P ＜ 0.05).Conclusion The first-episode schizophrenics have both sleep continuity and sleep structure deficits.Although olanzapine treatment can improve sleep quality,long-term use of it may cause overweight and sleep-breathing disorder.