The invention discloses a tandem type upright ladder for maintaining high-voltage lines. The ladder is characterized in that a chassis of the ladder is fixed by being matched with an outer conical surface at the lower end of a ladder post body via a middle inner cone hole; the outer conical surface of the ladder post body is fixed by being matched with an inner conical surface of the inner cone hole of the ladder post body; after the inner cone hole is fixed by being matched with the outer conical surface, the inner conical surface and the outer conical surface, which are jointed, are automatically locked by matching a brake groove in a lock rod with a shotpin; pedals are fixed on the surface of a post body of the ladder post body; anti-slip glue adheres to the pedals and the bottom of the chassis. The tandem type upright ladder for maintaining high-voltage lines has the beneficial effects that the ladder has a simple structure and is quite convenient to manufacture, assemble and use; tools are not needed in the assembling and dismantling processes during use of the ladder; after the tandem type upright ladder for maintaining high-voltage lines is adopted, the problem that high-voltage line maintenance men climb and stand uprightly is solved; the ladder for maintaining high-voltage lines is fast, convenient, safe and reliable to assemble during climbing and is convenient to climb; after being used, the ladder is convenient to dismantle, package and transport, thus reducing the production cost and the use cost.