Aims and objectives:To analyse the status quo and influencing factors of self-care ability in breast cancer-related lymphedema (BCRL) patients and explore the moderating role of social support between self-efficacy and self-care ability, to provide references for clinical intervention. Background:The 'gold standard' for the treatment of lymphedema is two-stage Complete Decongestion Therapy (CDT). Due to the high frequency of patients seeking treatment and CDT is not covered by medical insurance, resulting the medical cost is high, and a set integrated course of edema treatment cannot be completed.Nevertheless, with sufficient self-care ability, patients can reduce the frequency of outpatient and inpatient treatments, and initiate detumescence procedures with affordable home care. Accordingly, it is necessary to pay attention to the self-care ability of BCRL patients.Design: A descriptive and cross-sectional study following the STROBE guideline checklist.Methods: From June 2021 to January 2022, 156 BCRL patients were selected as convenience samples. Questionnaires were administered to the patients using the sociodemographic information questionnaire, the exercise of self-care agency scale, Chinese version of strategies used by people to promote health, and social support rating scale. Spearman rank correlation was used to analyse the relationship among the three, and univariate and multiple linear regression were used for factor analysis and process to explore the moderating role of social support. Results:The total score of self-care ability of BCRL patients was 41.00 (32.50, 51.00).The self-efficacy and social support of BCRL patients were positively correlated with the total score and its dimensions of self-care ability. Disease duration, severity and difficulty raising limbs were negative correlation factors influencing the self-care ability of BCRL patients, and self-efficacy and social support were positive correlation factors, which could explain 77.8% of the total variation. The moderating role of social support between self-efficacy and self-care ability was significant, and its moderating role boundary value was 15.70. Conclusions:The self-care ability of BCRL patients is at a low level. The longer duration of lymphedema, the more serious degree of edema, the more difficulty raising limbs, the lower self-efficacy and the less social support, the poorer self-care ability | 927 JIANG and CHEN