The present invention belongs to the field of medicinal chemistry, and relates to substituted pyrimidine compounds as phosphatidylinositol 3-kinase (PI3K) ?inhibitor and a use thereof. In particular, the present invention provides a compound as shown by formula I or an isomer, pharmaceutically acceptable salt, solvate or prodrug thereof, the preparation methods of same and pharmaceutical compositions containing these compounds and a use of these compounds or compositions for treating cancer, hyperblastosis diseases or inflammatory diseases. The compounds of the present invention have a good inhibiting activity on PI3K?and have a high selectivity. It is hoped that these will be therapeutic agents for cancer, hyperblastosis diseases or inflammatory diseases.