Taken a decommissioned Floating Production Storage and Offloading (FPSO) in an oil field as the research target, the towing analysis of the FPSO in time domain is carried out using the method of non-linear time-domain dynamic analysis and considering the combined effects of different environmental conditions. The towline tension response and FPSO yaw motion response are analyzed and studied. The results show that the maximum tension of the towline is less than the designed breaking load and the maximum yaw motion angle of the towed FPSO is close to 30^°under the given sea states. In the process of analysis, the system is in a stable state, and there is no numerical divergence. For conservative consideration, the tugboats are assumed to be fixed in the analysis, and the calculated results are conservative.