OBJECTIVE: To investigate the efficacy and timing of PDE-5i in the treatment of diabetic penile erectile dysfunction (DM-ED) of different disease duration. METHODS: One hundred patients with DM-ED, aged 38-61 years, mean 51.6 years, with DM duration of 2-12 years, mean 6.5 years, and ED duration of 1-10 years, mean 6.0 years, were included in the study. According to the DM-ED disease duration grouping: group A DM-ED disease duration 1-5 years, a total of 42 cases, the average age of 50.5 years; group B DM-ED disease duration 6-10 years, a total of 58 cases, the average age of 52.5 years. Both groups had good and smooth glycemic control. According to the International index of erectile function-5 (IIEF-5) score standard, the mean score before treatment was 14.5 in group A and 10 in group B. Patients in both groups were first given sildenafil 50 mg, QD×7d, and the improvement of IIEF-5 score was observed; if it was ineffective, patients in both groups were given sildenafil 100 mg, QD×7d, and the improvement of IIEF-5 score was observed; after one month, patients in both groups were given low-dose sildenafil 5 mg, QD×90d, and the improvement of IIEF-5 score was observed in both groups. Statistical analysis was performed to compare the improvement of IIEF-5 scores in the two groups. Results: There was no difference between the age of group A and B (P0.05); the difference between the IIEF-5 scores of the two groups before sildenafil treatment was statistically significant (P0.05); after sildenafil 50 mg treatment, patients in group A were effective and could obtain more satisfactory erection, and the IIEF-5 score improved to 21.5 (improved by 7 points), while patients in group B were effective, but erection was still not In group B, the IIEF-5 score increased to 13.5 (an increase of 3.5 points), p0.001 between the two groups; in group B, the IIEF-5 score increased to 16 (an increase of 2.5 points) after sildenafil 100 mg treatment; after long-term treatment with sildenafil 5 mg, the IIEF-5 score increased to 23.5 in group A3 and 19.5 in group B. The IIEF-5 score increased to 19.5 between the two groups. The longer the duration of DM, the greater the effect on penile erectile function, and the worse the response to PDE-5i treatment, the higher the dose requirement; long-term low-dose PDE-5i has a significant improvement on DM-ED, and its efficacy is negatively correlated with the duration of DM; early treatment with PDE-5i is advocated for DM-ED.