Numerical simulations on the AC loss characteristics in a thin high-temperature superconducting (HTS) tube are presented. Geometry of the HTS conductor is modeled as a tube with negligible thickness, and assumed to carry a transport current with the same phase as an AC exteally applied magnetic field perpendicular to the axis. Based on the classical theory of AC loss with the Bean critical current model, the distribution of critical current density jc and AC loss Q are obtained by means of numerical analysis. The results are in very good agreement with experiments. A double-peak profile is observed in the curve of the critical current density distribution along the azimuth angle. This numerical simulation method is suitable for a thin HTS tube, which may be applicable on a thin tube configuration consisting of coated superconductors.