Acoustic diode can control the sound wave in only one direction and cannot propagate in the opposite direction, which has potential application in communication technology.However, most of the current acoustic diode designs are based on nonlinear effects that make the system only through new high frequencies and prevent the transmission of the original frequency.In this paper, we use a combination of asymmetric structures and weak nonlinear phononic crystals to propose a onedimensional acoustic diode model that enables asymmetric transmission of elastic waves and keeps the frequency constant.The model consists of a variable amplitude rod at the left end and a nonlinear spring mass chain at the right end.Theoretical analysis shows that the acoustic diode has forward, reverse and breakdown properties very similar to those of the electron diode. This paper has demonstrated the model by finite element simulation.