The position and inclination of the mooring legs and yoke of a soft yoke mooring system for floating production storage and offloading in Bohai Bay were measured by full-scale monitoring technique. A novel multi-body dynamic analytical method of the horizontal restoring force for the soft yoke mooring system was established and investigated based on the monitoring data. The result predicted by the dynamic method agrees well with that obtained by fibre Bragg grating strain sensors. The peak value determined by the dynamic analysis is approximately 25% higher than that of the static results in harsh environments, which indicates the high reliability of the proposed method. After significant monitoring time, the advantages of the stability of the measurement by the proposed method are also manifested.