The utility model discloses a semitrailer carriage. The semitrailer carriage comprises a semitrailer carriage body, and the upper surface of a bottom plate of the semitrailer carriage body is 5 to 15mm higher than the upper surface of a lower side beam of the bottom plate. The semitrailer carriage has a simple structure; and water accumulation among a side plate, the bottom plate and the side beam of the semitrailer carriage is avoided.