In this paper, we investigate duality of modular g-Riesz bases and g-Riesz basesin Hilbert C*-modules. First we give some characterization of g-Riesz bases in Hilbert C*-modules, by using properties of operator theory. Next, we characterize the duals of a giveng-Riesz basis in Hilbert C*-module. In addition, we obtain sufficient and necessary conditionfor a dual of a g-Riesz basis to be again a g-Riesz basis. We find a situation for a g-Rieszbasis to have unique dual g-Riesz basis. Also, we show that every modular g-Riesz basis is ag-Riesz basis in Hilbert C*-module but the opposite implication is not true. پرونده مقاله