A method for separating ethylene oligomerization reaction products, comprising: introducing an oligomer fraction excluding unreacted ethylene and 1-butene among ethylene oligomerization reaction products into a cooling unit to be cooled; introducing the oligomer fraction discharged from the cooling unit into a first C6 distillation column to discharge a first upper fraction from a top of the first C6 distillation column and discharge a first lower fraction from a bottom of the first C6 distillation column; introducing the first upper fraction discharged from the top of the first C6 distillation column into a second C6 distillation column to discharge a second upper fraction from a top of the second C6 distillation column and discharge a second lower fraction from a bottom of the second C6 distillation column; and introducing the first lower fraction discharged from the bottom of the first C6 distillation column into a solvent distillation column to discharge a third upper fraction from a top of the solvent distillation column and discharge a third lower fraction from a bottom of the solvent distillation column, wherein the first C6 distillation column, the second C6 distillation column, and the solvent distillation column are each provided with a condenser and a reboiler, at least a portion of the oligomer fraction is used as a reboiler heat source for the solvent distillation column, and at least a portion of the third upper fraction is used as a reboiler heat source for each of the first C6 distillation column and the second C6 distillation column. introducing an oligomer fraction excluding unreacted ethylene and 1-butene among ethylene oligomerization reaction products into a cooling unit to be cooled; introducing the oligomer fraction discharged from the cooling unit into a first C6 distillation column to discharge a first upper fraction from a top of the first C6 distillation column and discharge a first lower fraction from a bottom of the first C6 distillation column; introducing the first upper fraction discharged from the top of the first C6 distillation column into a second C6 distillation column to discharge a second upper fraction from a top of the second C6 distillation column and discharge a second lower fraction from a bottom of the second C6 distillation column; and introducing the first lower fraction discharged from the bottom of the first C6 distillation column into a solvent distillation column to discharge a third upper fraction from a top of the solvent distillation column and discharge a third lower fraction from a bottom of the solvent distillation column, wherein the first C6 distillation column, the second C6 distillation column, and the solvent distillation column are each provided with a condenser and a reboiler, at least a portion of the oligomer fraction is used as a reboiler heat source for the solvent distillation column, and at least a portion of the third upper fraction is used as a reboiler heat source for each of the first C6 distillation column and the second C6 distillation column. at least a portion of the oligomer fraction is used as a reboiler heat source for the solvent distillation column, and at least a portion of the third upper fraction is used as a reboiler heat source for each of the first C6 distillation column and the second C6 distillation column.