Using nonequilibrium Green’s function and first-principles calculations, we investigate the effects of different molecular conformations induced by torsion angle on electronic transport and their stability in 4,4′-biphenyl bis (dithiocarboxylate) molecular junction under an applied electric field. The results indicate that there are two stable conformations existed in this molecular junction as external bias increasing. An electric field can be used to “switch” one conformation to the other, and there is an abrupt change in the degree of torsion angle in this process. This change is expected to cause a conductance switching in the system. Furthermore, the transport mechanism of this conformational molecular switch is discussed in detail.