Until recently the magnetomechanical behavior has been rather poorly understood with contradictory results and interpretations from different investigators in the study of stress monitoring by magnetic method. Based on the domain motion and field-induced magnetization process of magnetic material, the stress-induced magnetization process in two different magnetization states is analyzed in detail. Characteristics of the magnetomechanical behavior are revealed. Domain motion caused by stress always makes materials tend to stable state of free energy minimum and accordingly the magnetization will approach the anhysterestic magnetization. Moreover, it can be concluded that magnetization state is an essential factor influencing the magnetomechanical behavior. Experiments of magnetomechanical behavior for galvanized steel wire have been conducted for different magnetization state, and the results are in accord with the theoretical analyses. The magnetomechanical behavior is changed with magnetization state, which can be effectively used to explain the existing complex and diverse research results.