The present invention discloses a distributed electrical cross apparatus, and a system and method for the distributed electrical cross apparatus implementing an SNC cascade protection. The apparatus comprises a backboard and at least four single-boards integrated with electrical cross units, wherein the single-boards are inserted in the limited number of slots in the backboard, and these single-boards also set line-side service access units, client-side service access units and backboard access units. The present invention has both accessing of line-side services and accessing of client-side services in the same single-board, access and flexible scheduling of various services such as line-side services and client-side services and so on are implemented on the backboard with limited number of slots, and the function of the distributed electrical cross system processing various services is increased in the case of low cost. Moreover, the present invention not only performs protection switching for the sub-network with fault, but also can implement protection switching for the single-board with fault. As the multiplexing and de-multiplexing modules are introduced to process sub-wavelength level services, protection can also be performed for the sub-wavelength level service with fault.