The mechanical behavior and debonding process of pipe joints’ interface are the key points for pipe system. In order to better understand and describe the debonding failure of pipe joints subjected to torsional loads for safety design, the theoretical and numerical studies have been conducted. Firstly, based on the exponential softening bond-slip law, the analytical expressions of the interfacial shear stress and the load-displacement relationship at loaded end were obtained. Thus the shear stress propagation and the debonding progress of the whole interface for different bond lengths could be predicted. Secondly, a simplified interface bond-slip law was used by changing the exponential softening law into a bilinear model. The analytical solutions for the simplified model were also obtained. Based on the analytical solutions, the influence of bond length and stiffness on load-displacement curve and ultimate load were discussed. The stress transfer mechanism, the interface crack propagation and the ductility behavior of the joints were further explained.