The relation between the J-based mutual integral and the T-stress is derived. The mutual integral is shown to be evaluated without solving the boundary value problems. The T-stress, a useful parameter for crack stability, is thus obtained easily by a suitable application of the concept of the conservation integral. Two examples are presented; one is for the concentrated loadings on the crack surface of bimaterial interface and the other is for the edge loadings on sandwich specimen with interfacial crack.