The invention discloses a filling method of an anchor open caisson compartment for controlling subsection cable saddle displacement of a suspension bridge. The method has the following steps of: firstly, making an open caisson, reversing a hole opening on the wall of a rear compartment of the open caisson approaching close to the anchor tail, installing a working stand through the hole opening after the open caisson is sunk to the position, and installing a pipeline or a conveying belt; then, casting bottom-sealing concrete, and sealing the bottom of the open caisson; except the rear compartment of the open caisson, filling the other compartments; casting an open caisson cover plate and an anchor; and finally, erecting the cable, splicing steel box girders, paving the bridge surface, and filling the rear compartment of the open caisson through the pipeline or the conveying belt. By adopting the filling method, the filler weight at the rear part of the open caisson counteracts with thebending moment generated at the bottom center of the open caisson and the bending moment generated by the cable pull force when the bridge surface is paved, thereby controlling the displacement of the subsection cable saddle into within the minimum amplitude, and avoiding the large additional stress brought for the upper structure of the bridge.