Analytical calculation based on transmission line model is a classical method to study the circulation of submarine cables, but this method considers the submarine cable armour layer is a uniform whole layer structure, while the actual armour is made of metal wires (steel wires) stranded together, and it will lead to errors and reduce the accuracy of submarine cable circulation analysis. For this reason, an optimization method for the transmission line model of metal wire armoured submarine cable is proposed based on the improved whale optimization algorithm (IWOA). Firstly, a test platform based on the simplified substitution model of submarine cable is built, and the validity of the 2D finite element simulation model for calculating the circulation flow of submarine cable with metal wire armouring structure is verified based on the measured data, and then the IWOA algorithm is used to carry out the joint analysis of finite element-MATLAB, to obtain the electrical resistivity and magnetic permeability of the whole layer of the armouring after equivalence, and the analytical model of submarine cable transmission line reflecting the structure of the metal wire armouring is established based on the equivalence results. Taking the 220 kV submarine cable as an object for example analysis, referring to the finite element results, compared with the traditional analytical calculation method which directly reduces the wire armouring to the whole layer structure, the accuracy of induced voltage and ground loop current obtained by the method proposed is improved by 290 % and 40 %, respectively, and the absolute error is less than 4.9% and 1.3 %, respectively, and the computational efficiency is significantly higher than that of the finite element model.