  Topological nodal-line semimetals are always characterized by the drumhead
surface states at the open boundaries. In this paper we first derive an
analytical expression for the surface Green's function of a nodal-line
semimetal. By making use of this result, we explore the charge and spin
transport properties of a metallic chain on the surface of a nodal-line
semimetal, as functions of the gate voltage applied on the top of the material.
According to the size of the nodal loop, due to the coupling to the surface
modes, the charge conductance in the chain is found to show a robust plateau at
$e^{2}/h$, or to exhibit multiple valleys at $e^{2}/h$. Correspondingly, the
spin polarization of the transmitted current is $100\%$ at the plateau region,
or exhibits multiple peaks at nearly $100\%$. This feature can be viewed as a
transport signature of the topological nodal-line semimetals.
