The present invention relates to a class of phenylpyrimidone compounds, the pharmaceutical composition, the preparation method and the use thereof. More specifically, the present invention relates to a type of phenylpyrimidone compounds of the following formula I, the pharmaceutically acceptable salts or solvates thereof; and to the pharmaceutical composition as well as the preparation method of the said compounds. The said compounds of formula I according to the present invention can effectively inhibit type V phosphodiesterase (PDE5), and thus can be used for the treatment of various vascular disorders, such as male erectile dysfunction, pulmonary hypertension and the like.