In this paper, we proposed a VLSI architecture of the modified discrete cosine transform (MDCT) for MPEG 2/4 AAC encoders. The MDCT transforms the time domain input signals to the frequency domain spectrums. It is considered one of the most computational intensive part in implementing the AAC encoder. The AAC encoder allows four types of audio blocks while encoding the audio files. With our algorithm, the proposed design can share the coefficients needed in the MDCT. Moreover, we used a 2-dimensional folding technique to reduce the hardware cost while maintaining the audio quality. The proposed design is realized in TSMC 0.18-um 1P6M technology and is operated at 50 MHz. With these techniques on special hardware design, the result shows some advantages on low complexity.