Provided are a crystal form of a bromodomain protein inhibitor 2-[4-(2-hydroxyethoxy)-3,5-dimethylphenyl]-5,7-dimethoxyquinazolin-4(3H)-one represented by Formula I, a preparation method and a use thereof. The present invention belongs to the field of medicine.The crystal forms are crystal form CS2, crystal form CS8, crystal form CS13, crystal form CS20, crystal form CS1, crystal form CS7, crystal form CS9, crystal form CS11, and crystal form CS4, and can be used to prepare drugs for treating cardiovascular, cholesterol, or lipid-related disorders.