Objective：The current study aims to explore the role of serum soluble growth stimulation expressed gene 2（sST2）in evaluating the severity of connective tissue disease associated pulmonary arterial hypertension（CTD - PAH）based on simplified risk stratification. Methods：A total of 48 patients with CTD-PAH diagnosed by right heart catheterization（RHC）were included from the Departments of Rheumatology，the First Affiliated Hospital of Nanjing Medical University between Jan 2017 and Nov 2021. Baseline clinical evaluation，laboratory index，RHC parameters and treatment regimen were collected. Pearson and analysis linear regression were used for the correlation between clinical characteristics of CTD-PAH and sST2 level. A receiver operating characteristics（ROC） curve assessed the diagnostic value of sST2 in assessing low risk and intermediate-high risk CTD-PAH patients. Results：CTD-PAH patients in intermediate -high risk group was higher in sST2 level than low risk group[45.97（30.24，75.68）ng/mL vs. 29.36（20.89， 41.25）ng/mL，P=0.006]. ROC curve analysis showed that sST2≥45.56 ng/mL could identify intermediate-high risk CTD-PAH patients with a sensitivity and specificity of 56% and 91%，respectively. Conclusion：The sST2 is significantly associated with parameters that can reflect disease severity of CTD -PAH，and the sST2 level is signficantly higher in intermediate - high risk group than in low risk group. The measurement of sST2 may serve as a prognostic biomarker of CTD-PAH patients.