  In this paper we build the structure equations and the integrable systems for
a discrete centroaffine indefinite surface in $\R^3$. At the same time, some
centroaffine invariants are obtained according to the structure equations.
Using these centroaffine invariants, we study the Laplacian operator and the
convexity of a discrete centroaffine indefinite surface. Furthermore, some
interest examples are provided.
