Exploring molecular circuits with conductance modulation is of significant importance for constructing efficient molecular electronic devices. Novel through-space conjugated molecular wires based on naphthalene (Naph) are synthesized and their electronic structures, conductance behaviors and working mechanisms are investigated. The single-molecular conductance of Naph-based molecules measured by the scanning tunneling microscopy break junction (STM-BJ) measurement technique demonstrates that o-Naph possesses slightly higher molecular conductance compared with m-Naph by featuring through-bond and through-space conjugation. The flicker noise analyses and theoretical study confirm that the through-space conjugation in o-Naph plays a crucial role in charge transport. These findings demonstrate that the introduction of through-space conjugation is an effective and feasible approach to modulate single-molecular conductance.