The utility model provides a necking type cable passage for accomplish the passageway smoothly and arrange in limited space, conveniently transport maintenance simultaneously and repair, improve the cable passage utilization ratio. It includes the cable pit that is enclosed by cable trench support, characterized by, be the enclosed construction directly over the cable trench support, the top of cable pit sets up the throat, the upper portion of throat is little, the lower part is big the tip of throat sets up cable trench cover, just cable trench cover is located between two cubical switchboards or between cubical switchboard and the wall body. This passageway makes things convenient for upright operation of personnel, saves the construction and tours channel space to the cable passage degree of depth has effectively been reduced, leaving equitable perpendicular distance simultaneously, guaranteeing normally changing over to of personnel convenient operation and cable, the cable inlet wire is direct more, convenient and swift. Need not to dispose auxiliary facilities such as ventilation, illumination, fire prevention, saved the construction investment.