HYSY122 cylindrical FPSO is the first cylindrical FPSO independently designed and constructed in China. The layout of cushion piers is determined by analyzing the bearing capacity of the dock bottom and considering the structure of the hull bottom. Combined with the actual situation of the prefabricated and closed site and the structure characteristics of the cylindrical FPSO hull, a reasonable sectional and closed scheme is determined. Special construction schemes for pipelines and key equipment are formulated to meet the project requirements, so that the sectional prefabrication can be integrated to the greatest extent, ensuring the installation accuracy of key equipment, reducing the amount of high-altitude and closed space operations in the final assembly stage, and compressing the project period. Through the precision planning of the whole process of precision control, the overall precision control of the hull is strictly controlled within the required range. The plan meets the project requirements , the main hull construction was completed in 17 months, which has won more time for the hoisting integration of the upper module and system commissioning, and provides a technical reference for the company's subsequent similar projects.