Background: To evaluate the efficacy and safety of aildenafil citrate in the treatment of erectile dysfunction (ED) in Chinese population. Methods: A multicenter, randomized, double-blind, placebo-controlled, double-cycle crossover trial was conducted in three medical centers. Male patients with mild to moderate ED were randomized into two groups and received either aildenafil citrate or placebos, followed by a crossover administration after a 7-day washout. The primary outcome was the duration of penile rigidity over 60% measured by RigiScan (R) Plus. Main secondary outcomes were the duration of penile rigidity over 80% and erectile hardness score (EHS). Results: A total of 60 patients with mild to moderate ED were enrolled in the study and 57 of them completed the trial (30 in the aildenafil group and 27 in the placebo group). The median duration of penile tip rigidity over 60% was 4.25 (0.00, 19.00) min in the aildenafil group, as compared with 0.50 (0.00, 2.75) min in the placebo group (P<0.001). The median duration of penile base rigidity over 60% was 3.25 (0.00, 12.50) min in the aildenafil group, as compared with 0.00 (0.00, 2.50) min in the placebo group (P<0.001). The duration of penile base rigidity over 80% was significantly increased in the aildenafil group versus the placebo group (P=0.002). The EHS was significantly improved in the aildenafil group (P<0.001). No severe adverse events associated with aildenafil citrate occurred in both groups. Conclusions: These results suggested that aildenafil citrate was efficient and well-tolerated in the treatment of Chinese men with mild to moderate ED.