An Electro-Conjugate Fluid (ECF) is considered as a functional fluid like electro-hydro dynamics fluid, and it has a remarkable property that a jet flow is generated between two electrodes when a high voltage is applied to the electrodes. In this study two types of linear actuators consisting of the pistons and cylinders using an ECF are proposed. The one has a structure of a coil type electrodes, and the other has a structure of mesh type electrodes. The proposed actuators are fabricated, and their basic characteristics-such as piston velocities vs. applied voltages to electrodes and the load caracteristics are examined in the experiment. The experimental results show that the proposed linear actuators have the possibilities to be used as the functional linear actuators.