The invention discloses a horizontal loading test system for the bearing capacity performance of a U-shaped shield duct piece structure. The system comprises a duct piece support, a loading longitudinal beam, a reinforced concrete reaction wall, profiled steel reaction columns, a jack, an anchorage device, an active tensed steel strand and a passive tensed steel strand, wherein the duct piece support is provided with duct pieces which are spliced into a ring; a loading ring beam is arranged on the outer side of a duct piece ring; the loading ring beam is arranged on the outer side in a surrounding manner; the loading longitudinal beam is arranged on the outer side of the loading ring beam; the jack is arranged on the outer side of the loading longitudinal beam; the jack is connected with the reinforced concrete reaction wall through the active tensed steel strand anchored through the anchorage device; the reinforced concrete reaction wall is arranged inside the duct piece ring and is fixed through the profiled steel reaction columns; the profiled steel reaction columns are arranged on the inner and outer sides of the reinforced concrete reaction wall, and are connected with the jack through the active tensed steel strand anchored through the anchorage device; the profiled steel reaction columns are arranged on the inner and outer sides of the reinforced concrete reaction wall.