The present invention relates to a benzohetercyclic or benzoheteraromatic-cyclic derivative and a preparation method and application thereof in medicines, and particularly relates to a benzohetercyclic or benzoheteraromatic-cyclic derivative and a pharmaceutical salt thereof shown in general formula (I) and a preparation method and application thereof as MEK inhibitors especially as cancer therapeutic agents, and each substitution group in the general formula (I) is defined as specification definition. The compound provided by the present invention has good activity, and has a good resisting effect on the proliferation of tumor cells.