The utility model relates to a device is maintained to the power supply unit, and specifically speaking is an insulating cat ladder of combination formula in cabinet, its characterized in that is equipped with three section unit ladder frame at least, unit ladder frame comprises bracing piece and connecting rod that two root length degree are the same, the connecting rod both ends are connected the unit ladder frame that forms H shape with vertical shape's bracing piece middle part respectively, the both ends of bracing piece are equipped with the axis recess with the bracing piece coaxial line respectively, the bracing piece both ends of one of them unit ladder frame one side are equipped with the side recess that intersects vertically with the bracing piece axis respectively, unit ladder frame is through connector and the axis groove connection cat ladder that cheng insulates, unit ladder frame is through connecting piece and perpendicular recess, the axis groove phase connects into insulating halfpace, utilize clearance and space environment around equipment independent assortment and fixed between the equipment, have the equipment and dismantle the convenience, the operation is thus simple, advantages such as the support stability safety in utilization is good.