The invention discloses a device and a method for Viterbi decoding. The device comprises a path metric memory cell, an ACS computing unit and an address status mapper, wherein the path metric memory cell is used to store path metric of decoding state; the address status mapper is used to create path metric of decoding state and the mapping relation thereof in the memory address of path metric memory cell; the ACS computing unit is used to acquire path metric of decoding state from the memory address of path metric memory cell according to mapping relation to do computing update and return theupdated path metric value back to the original memory address. The method is to read and write path metric according to address status mapping relation. The invention can save memory space and effectively reduce the consumption of hardware resources.