The present invention relates to 6-(4-substituted-anilino)pyrimidine derivatives useful as an antiviral agent, and more particularly novel 6-(4-substituted-anilino)pyrimidine derivatives having an excellent inhibitory effect on replication of Hepatitis C virus; HCV), represented by the following formula I: ##STR00001## in which R represents a C.sub.1-C.sub.4 straight or branched alkoxycarbonyl group, heterocycliccarbonyl group or carboxyalkyl group; and pharmaceutically acceptable salts thereof, a preparation method thereof, and an antiviral pharmaceutical composition comprising the compound as an effective ingredient. The 6-(4-substituted-anilino)pyrimidine derivatives according to the present invention have an excellent inhibitory effect on replication of Hepatitis C virus (HCV) and thus can be advantageously used as a therapeutic or prophylactic agent of hepatitis C.