A numerical scheme, incorporated with the finite element method, is developed for calculation of the J2-integral for 2-D cracks appearing in rubbery fields under large deformation. The scheme is formulated based on the concept of the generalized version of the domain integral method. Due to the nature of J2 the method is shown to be "patch-independent" in a modified sense, and so the neartip region is always included in the calculation. The proposed technique is therefore particularly addressed to appropriate modeling of the near-tip singular mechanical behavior in order to circumvent the unavoidable imprecision aisociated with the finite element approximations in the vicinity of the crack tip. The numerical results show that no a priori information on the asymptotic singular behavior is required in order to achieve an acceptable value of J2. The computation procedure is generally feasible for different rubbery material models.