Umbilical cables are known as the "nerve lifeline" connecting underwater production systems and upper facilities, and accurate analysis of their temperature field distribution and ampacity is a key guarantee for safe offshore oil and gas exploration and production tasks. Unlike traditional submarine cables, umbilical cables have complex electro-thermal-fluid multi-physical fields coupling effects due to their complex structure and diverse functions, and it is difficult to determine their temperature field distribution and ampacity by traditional analytical methods. A fine cross-sectional model of multi-field coupling of umbilical cable was established based on the finite element software COMSOL in this paper, and the influence of three typical laying methods, environment and other factors on the conductor temperature and steady-state ampacity was studied by the control variable method. The results show that when the current is small, the temperature of the fluid in tube is the dominant factor affecting the cross-sectional temperature and steady-state ampacity of umbilical cable. The trend of conductor temperature can reflect the change of steady-state ampacity. When buried directly, the increase of buried depth and the external fluid temperature will weaken the heat dissipation capacity of umbilical cable. When tiled, the seawater flow significantly reduces the temperature of umbilical cable, and at low flow rates, the increase of flow rate has a significant cooling effect on the umbilical cable. However, the high flow rate of seawater will form a boundary layer with temperature gradient on the surface close to the umbilical cable, making the heat transfer be restricted, and the cooling effect is not obvious. The insulation ageing has less influence on the overall temperature distribution of umbilical cable, but it affects the maximum temperature of the cross-section.