NSFC [20931006, U0934003, 91122006]; NSF of Fujian Province [2011J01065] ; Single-molecule conductance of three sulphur-functionalized organometallic wires with two ruthenium(II) centres spaced by 1,3-butadiyne was firstly investigated using an electrochemically assisted-mechanically controllable break junction (EC-MCBJ) approach. It is demonstrated that single-molecular conductance of these diruthenium(II) incorporated systems is significantly higher than oligo(phenylene-ethynylene) (OPE) having comparable lengths and exhibits weaker length dependence. The conductance improvement in these diruthenium(II) molecules is ascribable to the better energy match of the Fermi level of gold electrodes with the HOMO that is mainly resident on the Ru-C C-C C-Ru backbone. Furthermore, modulation of molecular conductance is achieved by changing the length and pi-conjugated system of the chelating 2,2':6',2 ''-terpyridyl ligand.