It is an important topic for electronic packages to estimate the interfacial bonding strength between dissimilar materials. If it is not strong enough, delamination would arise easily under high temperature, vibration or collision. Its reliability will be reduced. The study on interfacial fracture behavior between epoxy resin and die based on experimental and numerical analyses is investigated, and it is useful to judge where the delamination happens . In terms of interfacial fracture mechanics, the critical strain energy release rate (G ) of crack tip is related to the phase angle (£r ) . Considering the interface of the epoxy /die existing a tiny crack, the compact mixed mode (CMM) fixture is used to decide the critical load . Finally , we adopt the finite element method to calculate that the critical strain energy release rate (G ) and the phase angle (£r ) in comparison with empirical results .