The purpose of this research is to find practical methods to predict the course stability of towed offshore structures at the initial design stage. The equilibrium yaw angles of a towed Floating Production Storage and Offloading (FPSO) with a single skeg and twin skegs are predicted by a drift model test and a Computational Fluid Dynamics (CFD) analysis. The results are compared with the towing model test results. Additionally, CFD towing simulations are performed and validated, and the mechanism of instability is analyzed through an investigation of physical quantities obtained from the CFD simulations.