In this work, we study some properties of weight matrices for the Dirac operator on a star graph, which are corresponding concepts to those of the Sturm-Liouville operator. There are two major ingredients. The first is devoted to the structure properties and asymptotic formulae of weight matrices. As an application, we construct a sequence of eigenfunctions and prove its Riesz basicity in the second ingredient. The methods employed rely on contour integration techniques and the theory of Riesz bases.