Electrochemical synthesis of ethylene from acetylene was put forward and the synthesized ethylene was characterized by gas chromatography (GC). First-principle calculations were carried out to examine the adsorption of acetylene over the Pd (111) surface. The electrochemical reduction behavior of acetylene has been investigated on a Pd electrode by cyclic voltammetry (CV) and stable polarization curves in sulfuric acid. The formation mechanism of ethylene in the sulfuric acid was proposed and the transfer coefficients of the reaction were calculated. The results showed that the acetylene molecule tended to be adsorbed through the threefold parallel-bridge configuration that was computed to be the most stable because of its lowest adsorption energy. The rate-determining step in the electrolysis process has been obtained. The rate of this step obtained from the assumed process agreed well with the experiment results.