Objective To explore the clinical effect and safety of sildenafil combined with bosentan in the treatment of connective tissue disease associated moderate-severe pulmonary arterial hypertension (CTD-MS-PAH ). Methods Seventy-six patients with CTD-MS-PAH during January 2013 to January 2017 were collected and divided into group A (41 cases) and group B (35 cases) using a stratified random sampling approach. The patients in group A received 25 mg sildenafil tablet therapy, three times a day. The patients group B received 25 mg sildenafil and 62.5 mg bosentan tablet therapy, twice a day. Both groups were treated for 12 weeks. Before and after the trial, all patients undertook six-minute walk test. Meanwhile the Borg dyspnea index score, the pulmonary artery systolic pressure (PASP), right ventricular diameter (RVD), B-type natriuretic peptide (BNP), the partial pressure of oxygen in artery (PaO2), blood pressure, heart rate, liver and kidney function were all measured. Results After the therapy, six-minute walking distance increased, Borg dyspnea index score decreased, PASP, RVD and plasma BNP decreased, and PaO2 increased in both groups (all P<0.05), but group B was superior to group A (allP<0.05). There were no significant differences in blood pressure, heart rate, liver or kidney function compared with those before the treatment in both groups (allP>0.05). Conclusion Sildenafil combined with bosentan can significantly decrease the level of pulmonary arterial pressure and effectively improve the cardiopulmonary function in CTD-MS-PAH patients with good safety.