Provided are a tricyclic derivative inhibitor, a preparation method therefor, and an application. In particular, the present invention relates to a compound as shown in general formula (I), a preparation method therefor, a pharmaceutical composition containing the compound, and a use thereof as a phosphoinositide 3-kinase (PI3K) inhibitor in the treatment of cancers and diseases or illnesses which are mediated by or dependent on PI3K imbalances.