The invention provides an installation process for an air conditioning outtake of a railway vehicle. The process comprises the following steps that: an installation seat, which horizontally extends into a passenger room, is welded on an upright column of a sidewall; a first limiting component and a second limiting component are fixed on the two sides of the outtake to form an outtake module; the outtake module is integrally mounted on the vehicle; the outtake module is placed on the installation seat and fixed by bolts; an outtake branch is in compression joint with an air inlet of the outtake, and the joint part is sealed by a sealing rubber strip; the outer end of an internally installed roof of the vehicle is inserted into a slot of the second limiting component; and the upper ends of internally installed side wallboards are overlapped on a bending part of the second limiting component. According to the process provided by the invention, the side roof, the side wallboards and the outtake are organically combined and reasonably connected, so that the space in the passenger room can be maximized, and the ride comfort of passengers is improved. The installation process provided by the invention has the characteristics that the installation time on the vehicle is short, the installation quality is high, and the maintenance is facilitated.