Abstract: Field coupling to transmission line is an important subject for electromagnetic compatibility analysis and electromagnetic effect evaluation. The classical models of field-to-transmission line coupling are limited by the quasi-TEM wave approximation, which leads to unacceptable model errors at higher frequencies. The transmission line super theory (TLST) has established the model of high frequency field-to-transmission line coupling and solved the difficulty of the classical models. Based on TLST the model of high frequency field coupling to the non-uniform multi-conductor transmission line is introduced in this paper. The boundary conditions in three cases of different terminal loads are also proposed. Finally, the results of some numerical examples of high frequency model are compared with the results of the classical models and the full wave analysis, which shows the universal applicability of the high frequency model, the validity of the boundary conditions setting and the correctness of the numerical implementation.