The design of the insulated core transformer(ICT)needs to consider the flux leakage effects.An equivalent linear circuit model is proposed based on the principle of duality.It is composed by two types of leakage inductances:conventional leakage between windings and special leakage introduced mainly by the insulation gaps.The values of leakage inductances depend on the dimensions of the core,gaps,or windings and the property of magnetic materials.The circuit allows for quantitatively evaluating influences of ICT internal parameters on its output properties.The winding self- and mutual inductance matrix is mathematically converted to derive the inductance formula.As an example,the leakage parameters of a sixstage two-dimensional(2D) ICT are calculated and analyzed. The design of the insulated core transformer (ICT) needs to consider the flux leakage effects. An equivalent circuit circuit is proposed based on the principle of duality. It is composed of two types of leakage inductances: conventional leakage between windings and special leakage introduced. mainly by the insulation gaps.The values ​​of leakage inductances depend on the dimensions of the core, gaps, or windings and the property of magnetic materials. the circuit allows for quantitatively evaluating influence of ICT internal parameters on its output properties. the winding self- and mutual inductance matrix is ​​mathematically converted to derive the inductance formula. As a example, the leakage parameters of a sixstage two-dimensional (2D) ICT are calculated and analyzed.