This study sought to investigate the clinical efficacy and safety of combined oral therapy with sildenafil and doxazosin GITS compared to sildenafil monotherapy in treating Chinese patients with erectile dysfunction (ED) and lower urinary tract symptoms secondary to benign prostatic hyperplasia (BPH/LUTS). The trial was conducted in hospitals in Beijing, Shanghai, Changsha, Wuhan and Guangzhou, five major cities in China. A total of 250 patients diagnosed with ED and BPH/LUTS aged 50-75 years, and who had International Index of Erection Function-5 (IIEF-5) scores ≤21 and International Prostate Symptom Score (IPSS) ≥10 points, were enrolled and randomly divided into Group A (168 cases; doxazosin GITS 4 mg once daily plus sildenafil 25-100 mg on demand) and Group B (82 cases; sildenafil 25-100 mg on demand). Efficacies were evaluated by IIEF-5 and IPSS scores and a quality of life (QoL) questionnaire, and adverse effects were evaluated during the treatment period. There were no statistically significant differences in mean age, and IIEF-5, IPSS and QoL scores pre-treatment between the two groups. After treatment, IIEF-5, IPSS and QoL scores were significantly improved in Group A, while only IIEF-5 scores were significantly improved in Group B compared with pre-treatment. There were no significant differences in side effects between the two groups. The results indicated that combined therapy with sildenafil and doxazosin GITS for the treatment of ED and BPH/LUTS is safe and effective compared to sildenafil monotherapy.