Pyrimidinone compound used as Lp-PLA2 inhibitor, and pharmaceutical composition of pyrimidinone compound

The invention relates to a pyrimidinone compound used as an Lp-PLA2 inhibitor, and a pharmaceutical composition of the pyrimidinone compound. The pyrimidinone compound has a structure as shown in a general formula I, wherein R1, R2, R3, X, Ar, Y and n are as defined in the specification and the claims. Stereoisomers or pharmaceutically acceptable salts of the compound as shown in the general formula I in the invention can be used as the Lp-PLA2 inhibitor to prevent and/or treat and/or improve diseases associated with LP-PLA2 enzymatic activity.