Abstract: Fault tree analysis (FTA) is applied to analyze the reliability of the subsea umbilical of a gas field in South China Sea both qualitatively and quantitively. The fault tree model of the subsea umbilical is built. The key components of the subsea umbilical are cable, sheath and armour according to the qualitative analysis result and the weakest link, also the most important component, is the cable based on the quantitive analysis result. Based on the analysis results, improvement measures focusing on the cable are put forward in terms of design, manufacturing and operation of the umbilical to reduce the risk of failure and improve the reliability of the umbilical, which is beneficial to the design and safe operation of the subsea umbilical.