Abstract: The basic deformation modes of a hybrid stress element are obtained by separating the stress modes corresponding to the different deformation modes of a hybrid stress element. Consequently a basic deformation-based approach is presented to investigate the performance for a given hybrid stress element. It is shown that the element deformation modes generally depend upon the assumed stress fields and thus are complex and coupled. In the proposed approach, the coupled stress fields are expressed with the stress parameters such that they can be easily decoupled into the linear combination of a series of basic stress fields. The relevant basic deformation modes are derived and the rigidity of hybrid element for arbitrary deformation modes, namely the element performance can be directly studied. The difficulty associated with the decoupling of various deformation modes is completely avoided. Investigations show that some of these assumed stress fields can not be used to the general hybrid elements.