The invention discloses a liquid distributor for a horizontal separator, and aims to solve the problems that according to an existing liquid distributor, an effluent liquid phase is at a rotational flow state, and liquid is not distributed uniformly. The liquid distributor is provided with a straight pipe (1), an expansion pipe (2) with a circular truncated cone surface shape, and a liquid distribution plate (3) with a sphere crown shape. The bottom part of the liquid distribution plate (3) is a non-opening area, and the other parts of the liquid distribution plate are opening areas provided with liquid distribution holes (7). The straight pipe (1), the expansion pipe (2) and the liquid distribution plate (3) form a liquid distributor shell; and a stand column (5) and vertically arranged rotation-stopping plates (6) are arranged in the liquid distributor shell. The rotation-stopping plates (6) are arranged around the stand columns (5); inner sides of the rotation-stopping plates (6) are connected with the stand columns (5); and outer sides of the rotation-stopping plates (6) fit to and are connected with an inner wall of the liquid distributor shell. The liquid distributor for thehorizontal separator provided by the invention is mainly used for liquid distribution of the horizontal separator, and can provide a favorable initial condition for gravitational separation of a horizontal type separation zone in the horizontal separator.