A new concept of thermal switch with liquid metal driven by electrowetting-on-dielectic (EWOD) was proposed in the first report. The thermal switch is expected to play a role of controlling both heat insulation and transfer in a heat transport system. Gallium alloy in place of mercury was utilized as liquid metal in this report. A treatment to inhibit oxide film formed in the surface of gallium alloy droplet was firstly evaluated. It was clarified that the method of putting a drop of diluted HCl in the surface of Gallium alloy droplet was effective in inhibition of oxide film. Then it was confirmed that a gallium alloy droplet was driven back and forth by EWOD.