The quasi-isotropic conductor stacked by the second generation (2G) high temperature superconducting (HTS) tapes is a promising choice for current transmission with low AC losses. In this paper, AC losses of quasi-isotropic conductor carrying a DC current in an AC magnetic field is studied by numerical and experimental methods at 77 K. AC losses are calculated by a two-dimensional finite element method (FEM) based on <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">T-A</i> formulation. Meanwhile, the total AC losses dissipated in the quasi-isotropic conductor can be obtained from experimental data of dynamic loss and the magnetization loss measured by electrical means. The amplitude of the external AC magnetic field and the DC transport current are varied. Simulation results are in good agreement with the experimental ones and the magnetic field distribution of the entire system is discussed in detail. The dependence of AC losses on external AC magnetic field and DC transport current is obtained, which is very helpful for fully understanding AC losses characteristic of quasi-isotropic conductors.