A drilling fluid additive composition, wherein the composition comprises a rheological modifier, an emulsifier and a tackifier, wherein: the rheological modifier is a dimer acid-organic amine copolymer comprising structural units from dimer acid, structural units from alkylamine and structural units from arylamine, of which the dimer acid is a dimer of oleic acid and linoleic acid, the alkylamine is one or more of C10-C20 alkyl primary amines, and the arylamine is one or more of aniline and aniline substituted by C1-C3 alkyl at one or more sites on benzene ring; the tackifier are modified polysiloxane nano-particles having a modifying Z group, and wherein the modifying group Z on the polysiloxane nano-particles is where, L is selected from C0-C6 alkylidene; the emulsifier is one or more of the compounds represented by the following Formula; in Formula, each of the two R 1 groups is independently selected from C14-C30 alkyl optionally substituted by group Y and C14-C30 unsaturated alkyl with a carbon-carbon double bond optionally substituted by group Y, and group Y is independently selected from the groups represented by the following formula: n is an integer of 1-8; n X-es are independently selected from H and -C -R 2, and at least one X is -C -R 2, R 2 is selected from carboxyl, C1-C6 alkyl, C3-C8 cycloalkyl, C1-C6 alkyl substituted by carboxyl, C3-C8 cycloalkyl substituted by carboxyl, C3-C8 cycloalkyl substituted by carboxyl and C1-C4 alkyl, C2-C6 unsaturated alkyl with a carbon-carbon double bond, C3-C8 unsaturated cycloalkyl with a carbon-carbon double bond, C2-C6 unsaturated alkyl with a carbon-carbon double bond substituted by carboxyl, and C3-C8 unsaturated cycloalkyl with a carbon-carbon double bond substituted by carboxyl and C1-C4 alkyl. the rheological modifier is a dimer acid-organic amine copolymer comprising structural units from dimer acid, structural units from alkylamine and structural units from arylamine, of which the dimer acid is a dimer of oleic acid and linoleic acid, the alkylamine is one or more of C10-C20 alkyl primary amines, and the arylamine is one or more of aniline and aniline substituted by C1-C3 alkyl at one or more sites on benzene ring; the tackifier are modified polysiloxane nano-particles having a modifying Z group, and wherein the modifying group Z on the polysiloxane nano-particles is where, L is selected from C0-C6 alkylidene; the emulsifier is one or more of the compounds represented by the following Formula; in Formula, each of the two R 1 groups is independently selected from C14-C30 alkyl optionally substituted by group Y and C14-C30 unsaturated alkyl with a carbon-carbon double bond optionally substituted by group Y, and group Y is independently selected from the groups represented by the following formula: n is an integer of 1-8; n X-es are independently selected from H and -C -R 2, and at least one X is -C -R 2, R 2 is selected from carboxyl, C1-C6 alkyl, C3-C8 cycloalkyl, C1-C6 alkyl substituted by carboxyl, C3-C8 cycloalkyl substituted by carboxyl, C3-C8 cycloalkyl substituted by carboxyl and C1-C4 alkyl, C2-C6 unsaturated alkyl with a carbon-carbon double bond, C3-C8 unsaturated cycloalkyl with a carbon-carbon double bond, C2-C6 unsaturated alkyl with a carbon-carbon double bond substituted by carboxyl, and C3-C8 unsaturated cycloalkyl with a carbon-carbon double bond substituted by carboxyl and C1-C4 alkyl. n is an integer of 1-8; n X-es are independently selected from H and -C -R 2, and at least one X is -C -R 2, R 2 is selected from carboxyl, C1-C6 alkyl, C3-C8 cycloalkyl, C1-C6 alkyl substituted by carboxyl, C3-C8 cycloalkyl substituted by carboxyl, C3-C8 cycloalkyl substituted by carboxyl and C1-C4 alkyl, C2-C6 unsaturated alkyl with a carbon-carbon double bond, C3-C8 unsaturated cycloalkyl with a carbon-carbon double bond, C2-C6 unsaturated alkyl with a carbon-carbon double bond substituted by carboxyl, and C3-C8 unsaturated cycloalkyl with a carbon-carbon double bond substituted by carboxyl and C1-C4 alkyl.