In order to design magnetorheological elastomers (MREs) based craftsmanship for metal forming, a comprehensive study on the mechanical properties of MREs under triaxial compression is required. An experimental setup integrating free compression and triaxial compression is designed to characterize isotropic MREs specimens under compression mode. The results showed that the MREs specimen in mold had successively experienced free compression stage, transition stage and triaxial compression stage during the experiment. The stress-strain curves of the MREs specimen changed when the concentration of magnetic particles increased from 0 to 44.7%, and the strain required to reach the transition stage was reduced. The effect of magnetic flux density on the stress-strain curves of the MREs specimen depended on the concentration of magnetic particles. The measured data obtained at different strain rates revealed maximum changes of 15.7% and 0.096% in volume compression modulus and Poisson ratio, respectively, which occurred under the magnetic flux density of 200 mT and CIP concentrations of [Formula: see text]. In this study, through a set of experiments, the stress-strain curves of the MREs specimen under different concentrations was elucidated, and their effects on the volume compression modulus and Poisson ratio were discussed.