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The effect of iron‐containing substances with different forms on the properties of carbon‐black filled natural rubber compound is discussed. The ionic iron substances (FeCl2, FeCl3, Fe(SA)3) have a detrimental effect on the rubber. Based on the oxidation induction temperature values, the relative deteriorating effects of ionic iron substances on the rubber are in the order: Fe(SA)3 > FeCl3 ≈ FeCl2. Not only are the metal ions (Fe2+, Fe3+) with adjacent stable oxidation states catalytically active in degrading rubber, but also the counterions have an influence on the effect of oxidation, particularly the stearic anion. Ionic iron materials can decrease the molecular weight, especially for the case of Fe(SA)3 as measured by gel permeation chromatography. Due to the degrading effect on the rubber molecules, Fe(SA)3 brings about a torque decrease in moving die rheometer and evident decrease of the Mooney viscosity at 100°C, which is different from the effects of Fe2O3 and 304L‐Fe. The insoluble iron substances behave more like hard fillers. Additionally, Fe(SA)3 remarkably alters the bound rubber content and the tensile properties after aging via two different process (scission and crosslinking). Overall, this work has a thorough comparison of effect of iron‐containing materials on rubber aging and provides useful inspiration to protect the rubber from deterioration by foreign reagents and regulating the rubber stability and degradation rate via introducing degradative metal ions. [ABSTRACT FROM AUTHOR]