This paper presents the fabrication and characterization of a new magnetorheological elastomer (MRE) by using polydimethylsiloxane (PDMS) as a matrix. The base and curing agent of PDMS with a weight ratio of 10:1 were mixed first as the carrying matrix, and then carbonyl iron particles were added to the matrix and stirred sufficiently. The final mixture was placed in a vacuum chamber to eliminate bubbles for 30 min and was moulded later to form membranes of 1 mm thickness. A total of four PDMS based MRE samples, with different weight fractions of 60%, 70%, 80%, and 90%, were fabricated. Their mechanical properties under both steady-state and dynamic loading conditions were tested. The effects of particle composition, magnetic field, strain amplitude and frequency on the MRE effects were summarized. With the increase of iron particle composition, the magnetorheological effects of the samples increase steadily. It is also noted that the initial modulus of the MRE samples shows an increasing trend with the iron particle composition. Additionally, the microstructures of the PDMS based MREs were also observed by a low vacuum scanning electric microscope (LV-SEM).