This study aimed to evaluate the efficacy and safety of long-term and low-dose tadalafil combined with sildenafil as needed at the early stage of treatment for erectile dysfunction (ED).We enrolled 180 patients with ED 1:1 to tadalafil 5 mg once daily or once-a-day tadalafil 5 mg combined with sildenafil 50 mg as needed.The efficacy measures included the 5-item version of the international index of erectile function (IIEF-5) and the sexual encounter profile (SEP).The safety was assessed by observing drug tolerability and adverse events.Total IIEF-5 scores of patients with severe ED in combined medication group were significantly higher than in tadalafil alone group.Question 2 scores of IIEF-5 of patients with moderate and severe ED in combined medication group were significandy higher than in tadalafil alone group.The significant improvement in question 3 scores of IIEF-5 existed only in patients with severe ED receiving combined medication.The percentage of yes responses to SEP4, SEP5 and partners SEP3 were improved significantly in combined medication group.There was no difference between two groups in the incidence of adverse events.Our results suggest that combined medication can better improve erectile function, especially for patients with severe ED.