In order to solve the hidden danger of potential oil leakage of swivel on FPSO, the swivel sealing replacement technology without FPSO heading restriction was studied with the example FPSO SPM swivel seal replacement project. From the aspects of weather conditions, shutdown duration and resource investment, the operation of sealing replacement between FPSO with and without heading restriction is analyzed. In the FPSO without heading restriction state, the rational design has been performed for the key processes such as the separation of driving arm, the disassembly and assembly of the support ring, the O-ring cutting and pasting, the chain rotation and other key steps. The practical results show that under the condition of FPSO without heading restriction, the operation of seal replacement has the advantages of low risk, low cost, simple construction and strong operability, and can successfully solve the construction issues of high precision, small space and high connection requirements of swivel seal replacement.Under the condition ofFPSO without heading restriction, the seal replacement technology has better economic efficiency and higher safety, which can be referred to by constructors.