Abstract: A device for joining floor tiles, having at least one joint unit; each joint unit has an L-shaped frame and a floor tile fixing plate; the L-shaped frame is provided with block members intersected with each other. The L-shaped frame is provided with inner engaging slots and outer engaging slots at an inner side and outer side respectively on upper surfaces of the block members. The inner engaging slots are engaged with inner engaging hooks disposed on the floor tile fixing plate. The outer engaging slots are engaged with outer engaging hooks on bottom sides of floor tile fixing plates of adjacent joint units. Also provided is an installation method of floor tiles.