A batch preparation system, comprising: an integrated reactor having an inner reaction space in which the direct esterification, which is the reaction of a first alcohol and a carboxylic acid-based compound comprising two or more carboxyl groups, and the trans-esterification, which is the reaction of the product of the direct esterification and a second alcohol, are carried out sequentially in the same space, an upper outlet line connected to a gas phase compartment, and a lower outlet line connected to a liquid phase compartment, provided therewith; a gas-liquid separation column having a gas-liquid separation space, into which a gasified reaction product and a gas phase low boiling point mixture from the integrated reactor flow through the upper outlet line of the integrated reactor and in which the gas-liquid separation is carried out, a lower recovery line, through which a liquefied reaction product is recovered to the integrated reactor, and an upper outflow line, through which the gas phase low boiling point mixture flows out, provided therewith; a purification unit having a purification bath, in which an ester composition flowed out through the lower outlet line of the integrated reactor and the second alcohol are separated, a purified product line through which a purified ester composition is discharged, and an alcohol recovery line through which the second alcohol is recovered, provided therewith; an alcohol storage tank having an inner space, in which the first alcohol and the second alcohol are stored, provided therewith, and connected to the upper outflow line of the gas-liquid separation column and to the alcohol recovery line of the purification unit, so as to store a mixed alcohol of the first alcohol and the second alcohol; and a mixed alcohol separation column having an alcohol separation space, into which the mixed alcohol flows from the alcohol tank and in which the mixed alcohol is separated depending on the number of alkyl carbon atoms of the alcohol, and one or more recirculation lines, through which separated alcohol is recirculated, provided therewith, wherein the reaction product in the gas-liquid separation column is a product of the direct esterification or a product of the trans-esterification, and the low boiling point mixture includes one or more of the first alcohol and the second alcohol, wherein the recirculation line of the mixed alcohol separation column comprises a recirculation line for the first alcohol and a recirculation line for the second alcohol, wherein the first and second alcohol are alcohols having one -OH group. an integrated reactor having an inner reaction space in which the direct esterification, which is the reaction of a first alcohol and a carboxylic acid-based compound comprising two or more carboxyl groups, and the trans-esterification, which is the reaction of the product of the direct esterification and a second alcohol, are carried out sequentially in the same space, an upper outlet line connected to a gas phase compartment, and a lower outlet line connected to a liquid phase compartment, provided therewith; a gas-liquid separation column having a gas-liquid separation space, into which a gasified reaction product and a gas phase low boiling point mixture from the integrated reactor flow through the upper outlet line of the integrated reactor and in which the gas-liquid separation is carried out, a lower recovery line, through which a liquefied reaction product is recovered to the integrated reactor, and an upper outflow line, through which the gas phase low boiling point mixture flows out, provided therewith; a purification unit having a purification bath, in which an ester composition flowed out through the lower outlet line of the integrated reactor and the second alcohol are separated, a purified product line through which a purified ester composition is discharged, and an alcohol recovery line through which the second alcohol is recovered, provided therewith; an alcohol storage tank having an inner space, in which the first alcohol and the second alcohol are stored, provided therewith, and connected to the upper outflow line of the gas-liquid separation column and to the alcohol recovery line of the purification unit, so as to store a mixed alcohol of the first alcohol and the second alcohol; and a mixed alcohol separation column having an alcohol separation space, into which the mixed alcohol flows from the alcohol tank and in which the mixed alcohol is separated depending on the number of alkyl carbon atoms of the alcohol, and one or more recirculation lines, through which separated alcohol is recirculated, provided therewith, wherein the reaction product in the gas-liquid separation column is a product of the direct esterification or a product of the trans-esterification, and the low boiling point mixture includes one or more of the first alcohol and the second alcohol, wherein the recirculation line of the mixed alcohol separation column comprises a recirculation line for the first alcohol and a recirculation line for the second alcohol, wherein the first and second alcohol are alcohols having one -OH group.