Based on the experimental results obtained from the undrained triaxial unloading tests of interlayer staggered zone (ISZ), the validity and applicability of five conventional strength criteria are investigated to describe the unloading failure and strength parameters of ISZ through the assessment indexes of the sum of absolute deviation. It is indicated that Mogi-Coulomb criterion has relatively low sum of absolute deviation and Euclidean norm, thus it has a preferable applicability to the description of the strength property of ISZ unloading failure, not only for the stress path of the axial and confining pressure unloading, but also for the course of loading axially and unloading of confining pressure. Considering the influence of the intermediate principal stress and the non-linearity of the Parabolic criterion with relatively high sum of absolute deviation and Euclidean norm, it is more complicated to calculate the derivative with less applicability. Mohr-Coulomb criterion may not be favorable to fit experimental results under higher confining pressure, and hence not be the best choice. Hoek-Brown criterion and Drucker-Prager criterion need to be carefully considered as the two criteria tend to cause the regression result to lack fidelity and cannot describe the strength property of unloading failure of ISZ. Although the above five strength criteria seem to be with high correlations (R² ≥ 0.95), the fitting deviations vary widely. Therefore, the correlation coefficient does not fully demonstrate the reliability of the criteria, which is suggested to combine with the least sum of absolute deviation to evaluate the applicability of unloading failure criteria of ISZ. The research lays the foundation for the selection of the plastic potential function and the solution of partial differential equations in the follow-up research.