The invention relates to a segmented later-installation-type stay cable main tower cable guide pipe structure which is formed by an internal tower cable guide pipe pre-buried in a tower wall and an external tower cable guide pipe installed after a main tower formwork is jacked. The bottom of the internal tower cable guide pipe is provided with a connecting plate which is flush with the outer side of the tower wall. A stiffening plate is arranged at the top of the external tower cable guide pipe. If the internal tower cable guide pipe is connected with the external tower cable guide pipe through bolts, the top of the external tower cable guide pipe also needs to be provided with a connecting plate; if the internal tower cable guide pipe is connected with the external tower cable guide pipe through welding, the connecting plate of the external tower cable guide pipe can be cancelled. The internal tower cable guide pipe is not exposed out of the tower wall, holes do not need to be formed in the formwork, and formwork jacking is not impeded; after the formwork is jacked, the external tower cable guide pipe is installed. By the adoption of the segmented later-installation-type stay cable main tower cable guide pipe structure, the holes of the cable guide pipes are not formed in the main tower formwork, the service cycle of the formwork can be prolonged, opening laying-out time is saved, the difficulty of formwork jacking is greatly reduced, and the site operation progress is accelerated.