Abstract: In order to improve the performance of heave compensation system of offshore drilling system, a dual-drawworks compensation scheme is proposed in view of single drawworks compensation systems. Through the dual-drawworks drum simultaneously driving the drill string, the motion of the drilling rig hoisting system is completely symmetrical, which provides the special advantages of high transmission efficiency and high safety. Then, to match the dual-drawworks scheme, a hoisting system scheme with variable rope system is designed, which can make the pulley blades on the traveling block symmetrical off the traveling block bracket from inside to outside in pairs, and locked on the crown block platform, so as to achieve the flexible transformation of rope system , and improve the working ability and efficiency of the system.