The present disclosure relates to novel crystalline forms of a bromodomain protein inhibitor 2-[4-(2-hydroxyethoxy)-3, 5-dimethylphenyl]-5, 7-dimethoxyquinazolin-4(3H)-one and processes for preparation and use thereof, relating to pharmaceutical industry. Form CS2, Form CS8, Form CS13, Form CS20, Form CS1, Form CS7, Form CS9, Form CS11 and Form CS4 of the present disclosure can be used for preparing drugs treating cardiovascular, cholesterol or lipid-related disorders.