Phosphodiesterases,an important class of catalytic enzymes,affect the corresponding biological function,by adjusting the ring of intracellular cyclic adenosine monophosphate(cAMP)and cyclic guanosine phosphate(cGMP).As a successful drug target,several drugs are developed based on inhibiting PDE5,one sub-class of PDE,which is mainly used for pulmonary hypertension and erectile dysfunction.However,drug development for this target slows significantly after 2011.In this review,we summarize the development of PDE5 and its inhibitors and briefly analyze the future development based on this target.