The environment of the South China Sea is very complex，and safety and precise positioning are urgent problems to be sloved in the process of using fiber ropes to lower subsea massive structure. Based on the small deformation theory, this paper proposes the basic theoretical model of fiber rope lowering, and tne lowering process of the installation of subsea massive structures at 3000 m depth in the South China Sea is simulated by using OrcaFlex software. The effects of wind speed, current velocity, wave height and wave direction on the tension of fiber rope and the motion deviation of the subsea massive structure are simulated and calculated. At the same time, the cable length when the fiber rope oscillation is explored. The results show that the wind speed and current velocity have slight impact on the tension of the fiber rope and the motion displacement of the object. Wave height and wave direction have great effect, and wave height is positive influence. Different wave directions have different degrees of effect. In addition, axial resonance occurs when the fiber rope is lowered to 610 m and 1040 m in the deepwater phase，at which time the installation operation needs special attention.