A robot-assisted endoscope system and control methods thereof allow a user to perform intraluminal interventional procedures using a steerable sheath. A processor generates a ghost image based on a non-real-time insertion trajectory of the sheath, and a real-time image based on a real-time insertion trajectory for inserting an interventional tool through the sheath towards the target site. A display screen outputs navigation guidance data for informing a user how to manipulate the distal section of the sheath towards the target site such that the real-time image overlaps or coincides with at least part the ghost image and the real-time insertion trajectory becomes aligned with the non-real-time insertion trajectory.