Objective To develop a peer support demand scale for patients with malignant tumor, and to test its reliability and validity,so as to provide an assessment tool for evaluating demand of peer support in patients with malignant tumor.Methods Guided by peer support theory,with theoretical review and qualitative interview,item pool of the peer support demand scale was preliminarily made. After a two-round expert consultation and preliminary scale investigation,first draft of the items was determined. 300 patients with malignant tumor were surveyed by the first draft of the scale,so that reliability and validity of the scale were tested.Results In the peer support demand scale for patients with malignant tumor,4 factors with 21 items were included,namely demands on peer support understanding,emotion,information and evaluation,The cumulative variance contribution rate was 59.684%. The content validity (S-CVI) was 0.920. Cronbacha′s α coefficient of the internal consistency reliability was 0.815,and the retest reliability was 0.824. Conclusions Content validity and internal consistency reliability are within acceptable range,which makes it basically qualified and can be used for investigation on patients with malignant tumor about their peer support demands.