Objective To investigate the characteristics of behavioral and psychological symptoms of dementia (BPSD) subsyndrome in patients with Alzheimer's disease (AD) and analyze the causes. Methods The demographic data, medical history and dietary habits of 137 patients with Alzheimer's disease who visited our hospital from January 2019 to October 2021 were collected by questionnaire. Excel 2007 and SPSS 22.0 software were used for statistical analysis of the occurrence of sleep disorders and BPSD subsyndrome. Multivariate logistic regression was used to analyze the influencing factors of its occurrence. Results There were 82 cases of sleep disorder (59.85%) and 118 cases of psycho-behavioral subsyndrome (86.13%) among those137 patients, of which 82 cases of sleep disorder mainly had low sleep quality (87.80%, 72/82), insufficient sleep time (73.17%, 60/82) and difficulty falling asleep (69.51%, 57/82); of which 118 cases of BPSD subsyndrome mainly had affective disorder (88.14%, 104/118), psychotic symptoms (76.27% , 90/118) and high activity (43.22% , 51/118). Multivariate logistic regression analysis showed that physical work , combined cerebral and cardiovascular diseases, dietary preference and severity of illness were the factors affecting sleep disorder (P<0.05) , while gender, residence, sleep disorder, whether the caregivers were full-time and severity of illness were the factors affecting the occurrence of behavioral subsyndrome (P<0.05). Conclusion Different types of sleep disorders and BPSD subsyndromes are common in patients with Alzheimer's disease. Attention should be paid to patients and intervention should be performed to improve their sleep and mental status.