PURPOSE: A method of separating 1,3-butadiene from C4 fraction using an acetylene conversion process is provided to reduce the time that foreign materials are generated. CONSTITUTION: A method of separating 1,3-butadiene from C4 fraction using an acetylene conversion process is as follows: A C4 fraction is supplied to a multi-stage hydrogenation reactor. The content of acetylenes is reduced under 70 wtppm by selectively converting acetylenes through a liquid-phase hydrogenation reaction. The fraction from the multi-stage hydrogenation reactor and an extractive solvent is supplied to an extractive distillation tower. A gas-phase fraction of the top of a pre-treatment separator is supplied to a solvent recovery tower, and a liquid-phase fraction of the bottom of the pre-treatment separator is supplied to a solvent stripping tower by applying a bottom fraction of the extractive distillation tower to the pre-treatment separator. The fraction from the solvent stripping tower, the fraction of butadiene and acetylenes, and the fraction of the pre-treatment separator are supplied to the solvent recovery tower. The overhead fraction of the solvent recovery tower is applied to a refining tower, and then, high purity 1.3- butadiene is obtained.