Objective: Based on simplified risk stratification to explore the value of serum soluble growth stimulation expressed gene 2 (sST2) level in evaluating the severity of patients in connective tissue disease associated pulmonary arterial hypertension (CTD-PAH). Methods: This retrospective cohort study enrolled 48 CTD-PAH patients diagnosed by right heart catheterization (RHC) during Jan 2017 and Nov 2021. Baseline and follow-up data collected including: demographic data, clinical data of CTD and PAH, treatment option of CTD and PAH. The risk grade was calculated according to a simplified risk stratification model based on 2018 world symposium on pulmonary hypertension (WSPH). The clinical baseline data of CTD-PAH patients, RHC parameters and sST2 level were analyzed by Pearson, and the correlated parameters were further linearly regressed. The ROC curve was used to analyze the optimal threshold of sST2 for identifying low risk and intermediate-high risk CTD-PAH patients. Groups comparison were performed by the log-rank test. Results: CTD-PAH patients with intermediate-high risk the sST2 level is significantly higher than low risk, 45.97(30.24-75.68)vs. 29.36 (20.89-41.25) ng/mL. ROC curve analysis showed that sST2≥45.56 ng/mL identify intermediate-high risk CTD-PAH patients with sensitivity and specificity were 56% and 91%, respectively. Conclusions: sST2 level can reflect the severity of disease in patients with CTD-PAH.