Objective: To study the changes of red blood cell distribution width (RDW) in connective tissue diseases-associated pulmonary hypertension (CTD-PH), and to explore the predictive value of RDW in patients with CTD-PH. Methods: The clinical data of 34 patients with CTD-PH admitted to the First Affiliated Hospital of NMU from January 2011 to December 2019 were retrospectively analyzed. According to the thresholds of RDW determined by ROC curve analysis, patients with CTD-PH were divided into high-level group and low-level group. Results: The cut-off value of RDW derived from the ROC analysis was 16.3% (area under curve = 0.729). The sensitivity is 66.7%, and the specificity is 84.0%. On COX regression analysis, RDW predicted death (P=0.04; HR 1.446; 95% CI 1.006-2.078). Compared with low-level group (RDW<16.3%), high-level group (RDW≥16.3%) shows a significantly high level of NT-proBNP (N-terminal pro B-type natriuretic peptide), a shorter TAPSE (tricuspid annular plane systolic excursion) and worse cardiac function. Conclusion: RDW is related to the long-term poor prognosis of patients with CTD-PH, which may be used as a potential prognostic marker for patients with CTD-PH.