This study investigated the electrochemical actuation behavior of nanoporous material during the capacitive process. The length change of nanoporous gold (npg) was in situ investigated in a liquid environment using the dilatometry technique. The mechanical effect of MnO layers was introduced in this work to improve the actuation characteristics of the npg samples. Our work found that the actuation behavior of npg sample could be significantly modulated with a covering of MnO layers. The electrochemical actuation amplitude was efficiently improved and strongly dependent on the thickness of MnO layers covered. Aside from the amplitude, the phase relation between the length change and the electrode potential was inverted when covering the MnO layer on the npg samples. This means the expansion of the npg samples and the contraction of samples covered with the MnO layer when electrochemical potential sweeps positively. A simple finite element model was built up to understand the effect of the MnO layer. The agreement between the simulation result and the experimental data indicates that the sign-inverted actuation-potential response of nanoporous gold contributes to the mechanical effect of MnO. It is believed that our work could offer a deep understanding on the effect of the MnO layer on the electrochemical actuation and then provide a useful strategy to modulate the actuation performance of nanoporous metal materials.