The invention relates to a pyrimidone derivative and application thereof. The pyrimidone derivative is a compound shown as a formula I or pharmaceutically-acceptable salt thereof. An activity inhibition experiment discovers that the pyrimidone derivative provided by the invention has a significant activity inhibition effect on dihydroorotate dehydrogenase of plasmodium falciparum. The invention lays a foundation for the preparation of a novel anti-malarial drug. In the formula I, R1 is a straight chain and a branched chain of C1-C6 or cyclic alkyl or amino; and A is a 5 to 6-membered saturatedor unsaturated carbocyclic group.