Abstract: A novel numerical boundary method, scaled boundary isogeomtric analys (SBIGA), is applied to fracture mechanics problem. Comparisons on accuracy and convergence rate in calculating stress intensity factor (SIFs) have been carried out for SBIGA and the scaled boundary finite element method (SBFEM). In contrast to SBFEM, NURBS is used to geometric modeling and boundary discretization in SBIGA. It is characterized by the following two aspects. Firstly, the model of boundary isogeometric representation can be imported from CAD directly. Thus, the time costs of mesh generation are saved and it avoids geometric approximation. On the other hand, it can be automatically refined without further communication with the CAD system and keeps geometry invariability. Adaptive analysis strategy can be employed conveniently for 2D problems. The numerical results show that, in comparison with SBFEM, more accurate result and higher convergence rate could be achieved through SBIGA. This is due to geometric accurate description, as well as higher order continuity of NURBS.