Abstract: Deepwater heavy lifting and subsea structure installation are the most important function of the deepwater semi-submersible crane and pipe-laying vessel, and reasonable function orientation of the main crane is essential to the design of the whole ship, the investment of the whole ship, and the market competitiveness. The weights of the offshore platforms and the subsea structures in China and abroad are statistically analyzed. The weights of the platforms at the East China Sea and the South China Sea are analyzed separately. The lifting analysis for platform at the target weight is conducted and the functional requirement analysis of the lifting operation is completed.