In order to study the bearing behavior of a single pile under combined loadings of horizontal force H and torque T, a loading device was first designed to apply H and T on the pile top simultaneously. 8 groups of indoor model were tested to obtain the inner forces and deformation as well as bearing capacities of the pile shaft. The result showed that, compared with the ultimate bearing capacity of pile shaft under pure H or T (i.e., Hu or Tu), the H-T load combinations with various magnitudes and sequences (i.e., H→T or T→H) caused an obvious decrease of the bearing capacity. For example, the application of 2Tu/3 on the pile top reduced the horizontal bearing capacity by 12.4 %, while the pre-loading of 2Hu/3 resulted in a reduction of the torsional bearing capacity up to 48.5 %. Therefore, traditional superposition principles can not be used in engineering design to evaluate the bearing capacity of piles under combined loads. Considering the effects of H-T combination and subsoil constraint on the torsional bearing capacity, the torsion angles at the pile top as well as the torque and moment distributions along the pile shaft were calculated by a MATLAB-based FEM program. The predictions were also compared with the model test data.