When the topside of the underwater soft yoke single point mooring system was installed at sea, it was found that the position of riser and the process pipe were misaligned. As a result, the pipeline assembly and welding cannot be completed, leading to offshore topside installation failure. In order to solve this problem, the failure-tree analysis was carried out for the misalignment of riser and process pipe. The implementation plan for the topside rectificationto be done onshore or offshore was proposed. Finally, offshore implementation was identified as the most optimal solution, determined via the perspective of implementation methods, resource input, vessel standby duration, construction cycle, construction characteristics and other analysis. The design for rectification option was rationalised taking into consideration the barge deck selection and riser rotation adjustment angle. At the same time, through project implementation, the construction process and key procedures of the topside installation of the underwater soft yoke mooring system were introduced. The experience and lessons-learnt of the topside offshore installation were summarized to provide references for the installation of single point mooring system of the same nature.