Disclosed are an iron-based catalyst and its application catalytic diene polymerization. The iron-based catalyst provided by the present application includes iron-containing organic compounds, alkyl aluminum compounds and isocyanide-containing organic compounds, and the molar ratio between the iron element of the iron-containing organic compounds, the alkyl aluminum compounds and the isocyanide-containing organic compounds is 1:(5˜100):(0.5˜100). The iron-based catalyst system of the present application can initiate polymerization of diene with high activity at high temperature by using isocyanide-containing organic compounds as an electron donor and alkyl aluminum compounds as a co-catalyst.