We present the Darboux transformations for a novel class of two-dimensional discrete integrable systems named as Z N graded discrete integrable systems, which were firstly proposed by Fordy and Xenitidis within the framework of Z N graded discrete Lax pairs very recently. In this paper, the Z N graded discrete equations in coprime case and their corresponding Lax pairs are derived from the discrete Gel'fand-Dikii hierarchy by applying a transformation of the independent variables. The construction of the Darboux tranformations is realised by considering the associated linear problems in the bilinear formalism for the Z N graded lattice equations. We show that all these Z N graded equations share a unified solution structure in our scheme.Key words and phrases. Z N discrete integrable system, Darboux transformations, tau function, discrete Gel'fand-Dikii hierarchy.1 Apart from the nonlinear forms given here, there also exist other nonlinear forms in the discrete KP family such as the discrete Schwarzian KP equation [24], the (2+1)-dimensional Nijhoff-Quispel-Capel (NQC) equation [25], and the various nonpotential versions of the discrete KP equations, see [26][27][28].