Abstract—An all-HTS motor is a promising device that can provide more compact size and higher performance than conventional motors. However, high AC loss in the HTS armature windings requires large cryogenic system which makes all-HTS motors impractical. This work numerically studied AC loss behaviours of the HTS armature windings in a 100 kW, 1500 rpm HTS motor. The model is based on COMSOL Multiphysics and T-A formulation. In order to investigate the real time electromagnetic behaviours, the moving mesh and rotating machinery interface are applied in this model. Preliminary results on magnetic flux distribution in the whole motor, current density in the HTS armature windings as well the AC loss are presented.