The invention provides a compound, a preparation method and an application thereof. The compound is a compound shown as the formula I or an enantiomer, a diastereoisomer, a racemate, pharmaceutically accepted salt, a crystalline hydrate or a solvate. The compound can be applied to preparing a medicine for treating cancer-related diseases, and particularly applied to preparing medicines for treating anaplastic lymphoma kinase-mediated non-small cell lung cancer. In the compound shown as the formula I, R1, R2, R3 and R4 are defined in the specification.