Abstract: A circuit model for magnetically insulated transmission line (MITL) based on TLCODE was established .In the model the MITL is divided into lots of lossy transmission lines, each of which comprises of a segment a lossless transmission line and a grounded resistor .According to the insulation theories, the states of these lossy segments can be identified and the related variables can be calculated. The interface voltage at the end of the MITL，which is necessary for TLCODE, is deduced from a wire array load. The solution process of the model is described. The comparison of the calculated results of Yang accelerator's MITL by the model with the experimental results indicates that the model is validated and is suitable for design and analysis of MITL.