Homoeomerous door-proof multi-function floor drain and its method of installation belong to technical field of homoeomerous discharge floor drain in architecture industry. The invention mainly provides a removable floor drain with water seals for surface drainage and pipe drainage. Its main programs are: set inlet and outlet on side of shell. One end of siphon is fixed-out in inlet and its other end is vertical downward. The cover board is on top of shell. The outer boss and the inner boss are fixed together. Set pinhole on center of grid plate, equip the upper boss matching the pinhole and locate a through hole on it. Middle and lower parts of encasing locates between concave stand and ectotheca. All around of encasing is fixed in positioning stand of inner casting. The installing steps are: after cleaning and drying, put the siphon and cover plate into the shell and encase the inner casting into the cover plate. Finally, enclose the encasing and grid plate together into the inner casting. The invention is applied in discharge branches or trunk, which has a bright prospect.