The present work was focused on the study of preparation a evaluation of properties of rubber magnetic composites based ethylene propylene diene monomer rubber EPDM as elastomeric matrix and strontium ferrite as magnetic filler. The mixed peroxide and sulfur curing systems were applied for cross-linking of rubber compounds. The research was aimed at the evaluation of the type of curing system on curing process of rubber compounds. Then, the influence of the observed parameter on cross-link density and physical-mechanical properties of prepared composites was investigated. The influence of thermo-oxidative ageing on the properties of tested composite materials was also under consideration. The achieved results showed that tensile strength was not dependent on the type of curing system, while cross-link density and physical-mechanical properties were changed in dependence on mutual ratio of sulfur and peroxide in the applied curing systems. Ferrite seems to act as a reinforcing filler in composites cured mainly with peroxide system, in which co-agent contributes to the improvement of compatibility and adhesion on the phase interface filler-rubber. The thermo-oxidative stability of composites was also found to be influenced by the curing system composition.