The present invention relates to a 1,2,4-triazine-3-amine derivative, a preparation therefor, and use thereof in medicine. Specifically, the present invention relates to a 1,2,4-triazine-3-amine derivative as represented by general formula (I), a preparation method therefor, a pharmaceutical composition comprising the derivative, and use thereof as a therapeutic agent, in particular as an A<;sub>;2a<;/sub>;receptor antagonist, and use thereof in the preparation of a medicament for treating a condition or disorder that is ameliorated by means of inhibition of the A<;sub>;2a<;/sub>;receptor, each substituent in general formula (I) being same as defined in the description.