Based on the principle of self-organization in Mach-Zehnder erbium-doped fiber laser cavity,charateristics of leak power are theoretically and experimentally demonstrated.One 3dB fiber loop mirror and a fiber Bragg grating with 4.5% reflectivity are used as cavity mirrors.A high coherent combining efficiency of 93.5% was obtained.Research on characteristics of leak power opens out self-organization mechanism in Mach-Zehnder compound cavity.Many applications to coherent combining high power lasers are expected.