The present invention belongs to the field of pharmaceutical Chemistry. In particular, the present invention relates to a pyridopyrimidine or pyrimidopyrimidine compound as represented by general formula (I), or an isomer thereof or a pharmaceutically acceptable salt, ester, prodrug or solvate thereof, a preparation method, a pharmaceutical composition and uses thereof in preparing a mTOR inhibitor. As a mTOR inhibitor, the compound or the pharmaceutical composition thereof can be used for treating a disease or condition due to PI3K-AKT-mTOR signalling pathway malfunction.
