For the purpose of a better understanding of the mechanical behavior of pipe joints’ interface which is critical for the integral performance of a pipe system, and excessive torsional loading that is typical for their interfacial failure, the interfacial behavior of adhesive bonded pipe joints under torsion loads is theoretically studied throughout the full-ranged failure process based on a local bond-slip law with hardening and exponential softening. Firstly, closed-form solutions for the interfacial shear stress distribution and load–displacement response are derived to describe the four basic loading stages. Secondly, a simplified law is used by changing the exponential softening law into a tri-linear one to make the comparison. According to the analytical solutions of two laws, the influences of the bond length on load–displacement curve including the ultimate loads and relative slips are discussed, with the similarities and differences between the two laws being studied. Thirdly, by introducing a dimensionless damage parameter, the results of the finite element method (FEM) using ABAQUS modeling are compared with analytical results. Based on these coincident results, the parametric studies of bond lengths and ratios of torsion stiffness on specific cases were conducted to explain the stress transfer mechanism and interface crack propagation. Both their ultimate bearing capacity and ductility improve in an increase of bond lengths, while the ductility reduces as the ratio of torsion stiffness increases. The outcomes of this paper are helpful to improve the safety and applicability of bonded pipe joints in engineering design and application.