Abstract: The address generation unit(AGU) is an important part of DSP,which can improve the efficiency of instruction execution by supporting multi-addressing modes.This paper introduces the addressing mode of an embedded DSP and the structure of its addressing instruction coding in detail.According to it,the AGU of the DSP has been designed and realized,which can support several especial addressing modes and thrice addressing operations in one cycle.The results of optimizing this AGU show that it has not only improved the performance and saved the power dissipation but also reduced the execution cycles of digital signal processing arithmetic.