In this paper, we studied the eigenspace of the regular differentials on a connected nodal curve $X$ under the action of a finite automorphism group $G$. We proved that the dimension of the space of $G$-invariant regular differentials is the arithmetic genus of the quotient nodal curve $X/G$. In addition, we generalized the Chevalley-Weil formula to nodal curves in the case where $X/G$ is smooth and gave some examples.