In this paper we obtain the coupling coefficient of plasmonic directional coupler (PDC) made up of two monolayer waveguides separated in the range of 200 nm for TM mode and we assume each waveguides acts as a perturbation to other waveguide but does not affect the waveguide mode.  We numerically calculated the Transfer distance respect to normalized frequency and simulated in two directions,  and z, values are about millimetres and smaller in a limitation of a bandwidth. Thus it is suitable for designing of integrated optical circuits and construction of couplers and switches.