A drilling fluid additive composition, comprising a lubricant, an emulsifier, and a rheological modifier, wherein the lubricant contains: graphite oxide and a biquaternary ammonium salt compound of which the cation part is represented by formula: or a biquaternary ammonium salt compound linked to the surface of the graphite oxide in the form of a modifying group, of which the cation part is represented by formula: wherein, each R 1 group is independently selected from H, hydroxyl, halogen, C1-C6 alkyl, C1-C6 alkoxy, and C1-C6 hydroxyalkyl; each R 2 group is independently selected from H and C1-C6 alkyl; each R 3 group is independently selected from H, C1-C20 alkyl, and C1-C20 hydroxyalkyl; the emulsifier is one or more of compounds represented by formula: in the 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 carbon-carbon double bonds optionally substituted by group Y, and the group Y is independently selected from the groups represented by the following formulae: n is an integer in a range 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. graphite oxide and a biquaternary ammonium salt compound of which the cation part is represented by formula: or a biquaternary ammonium salt compound linked to the surface of the graphite oxide in the form of a modifying group, of which the cation part is represented by formula: wherein, each R 1 group is independently selected from H, hydroxyl, halogen, C1-C6 alkyl, C1-C6 alkoxy, and C1-C6 hydroxyalkyl; each R 2 group is independently selected from H and C1-C6 alkyl; each R 3 group is independently selected from H, C1-C20 alkyl, and C1-C20 hydroxyalkyl; the emulsifier is one or more of compounds represented by formula: in the 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 carbon-carbon double bonds optionally substituted by group Y, and the group Y is independently selected from the groups represented by the following formulae: n is an integer in a range 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.