Complexity reduction method of MPEG-4 ER-BSAC audio decoder is proposed in this paper BSAC audio codec is standard audio codec of terrestrial DMB. Terrestrial DMB receiver is a digital signal processor(DSP) in this paper. When BSAC audio decoder is ported on DSP, floating point operation takes so long time in fixed point processor. The filter bank module takes a lot of time since it has many floating point operation in this module. Thus, in this paper, the floating point operations of filter bank module are converted to fixed point operations. And floating point operations of PNS and TNS part also are converted to fixed point operations. And many repetition structure are unrolled by unrolling method and nisu inline function. The proposed method performed better than former process.