For the limitation of single-wavelength laser interference in military electro-optical countermeasure, the composite output program of dual-wavelength laser was proposed, providing an efficient way for universalization of military electro-optical countermeasure equipment. With the theory of steady state and rate equation, the composite output model in both continuous and pulsed output conditions were established. The result of numerical simulation shows that there exists optimal KTP length in both continuous and pulsed conditions. While the best fundamental-wavelength(FW) transmissivity only exists in continuous condition. Through the experiment, the relationship between FW transmissivity and output ratio of composite laser was verified. The effect of repetition rate on output ratio is then explored in experiment.