To investigate the effect of phosphodiesterase type 5 (PDE5) small interfering RNA (siRNA) on cyclic guanosine monophosphatethe (cGMP) in the smooth muscle cells of human corpus cavernosum, and to provide laboratory evidence for the application of the RNA interference (RNAi) technique for the treatment of erectile dysfunction.The recombinant adenovirus rAd5-shRNA-PDE5A3 expressing three pairs of specific shRNA was constructed successfully. The smooth muscle cells of human corpus cavernosum were divided into an experimental, a negative control and a blank control group, and transfected respectively with rAd5-shRNA-PDE5A3, adenovirus rAd5-mock and phosphate buffered saline. The concentration of cGMP was measured by radioimmunoassay at 24, 48 and 72 hours after transfection, and the effect of rAd5-shRNA-PDE5A3 was detected on the cGMP in the smooth muscle cells of the corpus cavernosum.The cGMP level in the smooth muscle cells of the corpus cavernosum was significantly higher in the rAd5-shRNA-PDE5A3 group than in the rAd5-mock control and blank control groups (P < 0.05), most significantly at 72 hours after transfection.The rAd5-shRNA-PDE5A3 can obviously increase the cGMP level in the smooth muscle cells of human corpus cavernosum, and enhance the inhibition of the PDE5 gene.