The invention discloses a bridge composite foundation consisting of an open caisson and a pile and a construction method and relates to bridge technology. The composite foundation consists of the open caisson and the pile. Open caisson partition walls have horizontal and longitudinal wall structures. A pile sinking preformed hole is reserved at the intersection of the open caisson partition walls. A steel pipe pile or a concrete driven pile sinks through the hole. The construction method comprises the following steps of: manufacturing the first section of the open caisson, floating the first section to a bridge position designed position, positioning the first section, filling water into an open caisson wall and the partition walls to sink the pile, heightening the section until the open caisson sinks to position, and casting concrete into the open caisson wall and the partition walls; after the open caisson sucks mud to sink, continuously heightening the section, and casting open caisson bottom sealing concrete when the open caisson is heightened to a designed standard height; riprapping the periphery of the open caisson to protect the open caisson, pumping water from the open caisson or coring the open caisson, and constructing an open caisson top plate; and after sinking the pile in the pile sinking preformed hole, casting the concrete into the pile sinking preformed hole to realize connection between the open caisson and the pile. The bridge composite foundation of the invention is suitable for a deep water soft soil foundation, takes the advantage of the open caisson having high rigidity and serving as a pile foundation construction space enclosing structure and exerts the characteristic of controlling sinking of the pile foundation.