Abstract: As the power load and the demand of power supply reliability continue to increase, accurate and rapid evaluation of transient temperature rise is helpful to improvement in the management level of dynamic load and emergency load. According to uniqueness of temperature field, an equivalent two-branch transient thermal circuit model was provided to represent the complex cable structure and environment. Because of the similarity of electrical circuit and thermal circuit, a transient adjoint model of thermal capacity and nodal admittance matrix of the transient thermal circuit model were built by transient analysis method of lumped parameter network in circuit. The nodal temperature rise equation was built too. It is not easy to calculate the thermal capacity of thermal resistance of transient thermal circuit, therefore, the thermal parameters of transient thermal circuit model were obtained by adopting the particle swarm optimization and transient analysis method of transient thermal circuit model. The fitness function of particle swarm optimization is the sum of square of difference between transient thermal circuit model results and finite element analysis results or trial results. Because of the heat transfer delay characteristic of buried power cable, the transient thermal circuit model was separated to short time model and long time model. The transient temperature rise of step current and cyclic current can be calculated accurately and rapidly. The comparison of finite element analysis results and trial results prove that the transient thermal circuit model possesses high accuracy and is helpful to improvement in the management level of transient load.