AC loss is one of the most crucial issues in the high-temperature superconducting (HTS) cables which carry large currents. In recent years, various numerical simulation techniques have been implemented to investigate the AC loss of the HTS cables under applied field and transport current, such as H formulation, T-A formulation, and J integral formulation. However, the H formulation has a problem that it is not easy to set the boundary conditions imposing the transport current in 3D simulation, while the T-A formulation simulates some 3D complex geometries, such as CORC cables, because of the appearance of small gaps, its computational efficiency is comparable to that of H formulation. But the integral method can avoid these two problems very effectively because the air domain is not required. In this paper, we use the T integral formulation with the current density vector T as the state variable, which has fewer unknowns compared to the J integral formulation. However, the integral methods have been considered for a long time to be inappropriate for large-scale problems, due to the dense matrices. To solve this problem, this paper applies the fast multipole method (FMM) to accelerate the T integral formulation, which avoids the generation of dense matrices and improves the computational speed. This paper first compares the computational efficiency of the T integral formulation and the T-A formulation through the 2D interface of the CORC cable and verifies the effectiveness of the T integral formulation in large-scale problems with the help of the FMM. Then, the approach is extended to AC loss calculation for the 3D HTS cables.