A coupled-mode theory for treating the coupling of two terahertz (THz) wire waveguides was studied using the coupled-mode assumption.Both coupling equations and coupling coefficients were obtained by using approximations equivalent with those in coupled-mode theory of optical waveguides.Furthermore,the solutions and coupling characteristics of coupled-mode equations for two same wire waveguides were obtained.The present theory is useful for treating problems involving energy exchange between the wire waveguides.