An apparatus for processing an audio signal and method thereof are disclosed. The apparatus comprises an information receiving unit receiving a downmix signal including and a plurality of preset informations; an external preset information receiving unit receiving a plurality of external preset informations being inputted from external; an external preset applying-determining unit determining whether the plurality of the external preset informations applies to the downmix signal; an external preset information selecting unit selecting one external preset information, if the plurality of external preset informations is selected; and a rendering unit controlling the object by applying the external preset information to the all data regions.Accordingly, an audio signal can be efficiently reconstructed by individually selecting and applying external preset information by a data region unit or by selecting and applying the same external preset information to a whole downmix signal. And, feedback information can be received from a user by displaying an object adjusted by having external preset rendering parameter applied thereto on a screen, according to a characteristic of an audio source.