Abstract: A method and apparatus for erecting and removing offshore structures including a jacket and a platform is disclosed. The system of the invention includes a platform-lifting unit, a jacket lifting unit, and a control unit. The platform-lifting unit includes a laterally and vertically movable truss member, which is hingedly connected to a barge with lifting beams, and a means for positioning the truss member at desired height and at lateral displacement above the barge. The jacket-lifting unit contains a ballast tank structure connected to a strong back that has a plurality of grappling members. The control unit contains all supporting and controlling systems for the other units. To remove the platform, the truss member of the platform lifting unit is moved underneath the platform, the truss is raised to exert force on the platform, the platform is severed from the jacket, and the platform is moved on top of the barge.