Method for preparing 1,3-butadiene as high yield

A method for preparing 1,3-butadiene as a high yield comprising the steps of a) charging a first catalyst in a first reactor as a catalyst fixed bed, b) charging a second catalyst into a second reactor connected to the first reactor in parallel as a catalyst fixed bed, simultaneously or sequentially with step (a), c) performing the oxidative dehydrogenation, by passing continuously low-boiling point fraction contained mainly 1-butene obtained through a distillation column from a C4 mixture containing normal butene, together with an air and steam through a catalyst layer of the first reactor, while performing the oxidative dehydrogenation, by passing continuously high-boiling point fraction contained mainly 2-butene together with air and steam through a catalyst layer of the second reactor, and d) separating and purifying 1,3-butadiene, the normal-butene and other C4 mixture obtained from the first reactor and the second reactor.