Abstract： Objective:To construct a parallel mediation model from the perspective of symptom clusters to verify the mediating effect of sleep disorders and depression in the relationship between pain and fatigue in elderly malignant tumor patients, and explore the pathways and relationships of the internal symptoms of fatigue associated symptom clusters.Methods:From January to April 2022, convenience sampling was used to select 312 elderly patients with malignant tumors from Beijing Hospital as respondents. General Information Questionnaire, Numerical Rating Scale, Pittsburgh Sleep Quality Index, Hospital Anxiety and Depression Scale, and Cancer Fatigue Scale were used for measurement. Spearman correlation was used to explore the correlation between pain, fatigue, depression, and sleep disorders, AMOS 24.0 was used to construct a parallel mediation model, and Bootstrap method was used to test the mediating effect.Results:A total of 312 questionnaires were distributed, and 305 valid questionnaires were collected, with an effective response rate of 97.76%. Pain of elderly patients with malignant tumors was positively correlated with fatigue ( r=0.436, P<0.01), sleep disorders ( r=0.316, P<0.01), and depression ( r=0.315, P<0.01), sleep disorders were positively correlated with fatigue ( r=0.491, P<0.01), and depression and fatigue were positively correlated ( r=0.587, P<0.01). The mediation model included two pathways: sleep disorders and depression partially mediated the relationship between pain and fatigue, accounting for 40.63% (0.221) and 14.89% (0.081) of the total effect (0.544), respectively. The total mediating effect was 55.51%, which was higher than the direct effect of 44.49%. Conclusions:There is a parallel mediating effect of pain-sleep disorder-depression-fatigue within the fatigue associated symptom cluster (pain, sleep disorders, depression, fatigue) in elderly malignant tumor patients. Medical and nursing staff can alleviate fatigue symptoms by improving the patient's pain condition and reducing their sleep disorders and depression symptoms.