Icariin is an effective monomeric compound extracted and purified from the traditional Chinese medicinal herb Epimedium (Icaritin, also known as “Akoradine”). Icaritin acts on immune-related signaling pathways and exerts its unique anti-tumor effects through anti-inflammatory, immune function regulation, and tumor microenvironment improvement. From the perspective of modern medicine, the classical tumor immunotherapy theory of “Fuzheng treatment principle” was verified. It has been reported that PDE5 phosphodiesterase (PDE5) has a strong inhibitory activity. PDE5 plays an important role in the pathogenesis of PAH and has the aphrodisiac effect of linafil.