Phosphodiesterase type-5 inhibitors (PDE5-Is) have been recommended as first line therapy for erectile dysfunction for patients received nerve-sparing radical prostatectomy for prostate cancer. We examed the efficiency of PDE5-Is and considered the optimal application. Systematic search of PubMed, Embase and the Cochrane Library was performed to identify all the studies. We identified 103 studies including 3175 patients, of which 14 were recruited for systematic review. Compared with placebo, PDE5-Is significantly ameliorated the International Index of Erectile Function-Erectile Function domain score (IIEF) scores (MD 4.89, 95% CI 4.25-5.53, p < 0.001). By network meta-analysis, sildenafil seems to be the most efficiency with a slightly higher rate of treatment-emergent adverse events (TEATs), whereas tadalafil had the lowest TEATs. In terms of IIEF scores, regular regimen was remarkably better than on-demand (MD 3.28, 95% CI 1.67-4.89, p < 0.001). Regular use was not associated with higher proportion of patients suffering TEATs compared with on-demand (RR 1.02, 95% CI 0.90-1.16, p = 0.72). Compared with placebo, PDE5-Is manifested significantly improved treatment outcomes. Overall, regular regimen demonstrated statistically pronounced better potency than on-demand. Coupled with the comparable rate of side effects, these findings support the regular delivery procedure to be a cost-effective option for patients.