In the experiments of the output characteristic from a multiple-electrode-pair laser, keeping the discharge parameters (such as pressure, voltage, discharge volume and so on) changeless, when several electrode-pairs are triggered in the same time, the laser pulse energy enhances nonlinearly. The experimental rules are summed up and the effects of the interaction of several discharge sections on the intracavity photon density and cavity efficiency are considereds and the reasons of nonlinear energy enhancement are analyzed, and a theoretical model is set up. The theoretical analysis agrees with the experiments.