Phosphodiesterases themselves are enzymes, capable of catalyzing many active processes in the body. According to the classification of phosphodiesterase itself, inhibitors are also classified, the abbreviation of phosphodiesterase is PDE, the first is PDE1 inhibitor, that is, inhibitors of phosphodiesterase 1, mainly vasodilating effect. Although divided into 1, 2, 3, 4, 5, 6, 7, 8, different types, but the main mechanism of action is to increase the concentration of intracellular cyclic guanosine phosphate, thus playing the role of vasodilatation, increase myocardial contractility, anti-inflammatory, anti-platelet. Therefore, if PDE1 is inhibited, the main effective effect is vasodilatation, PDE2 is mainly antiplatelet, PDE3 inhibitors are mainly used to enhance myocardial contractility for the treatment of heart failure. PDE5 inhibitors are commonly used to improve sexual function. There are also other types of drugs that improve immunosuppression, such as PDE4, PDE7, and PDE8. These drugs are widely distributed in the clinic and have a wide range of effects, and are generally chosen for their suitability for use in different diseases.