Abstract: The three-core submarine cable is an important device connecting offshore wind farms with land power grids, and its normal operation is of great significance to economic development. The relationship model between conductor temperature and fiber temperature is the theoretical basis of temperature distributed sensing, and the influence of twisting of optical fiber and cable on the relationship between conductor and optical fiber temperature is rarely taken into account in previous studies. Based on the finite element method, the electrothermal flow coupling model of three-core composite optical fiber submarine cable considering twisting is constructed, the relationship between conductor temperature and optical fiber temperature is obtained, and the effects of pitch, seawater temperature, seawater surface heat transfer coefficient and different cable sizes on the conductor and fiber temperatures under the buried and laying environment are analyzed. The simulation results show that, under the buried conditions, when the twisting is not considered, the conductor rises by 1.03 ℃, and the fiber rises by 1.00 ℃; moreover, when the twisting is considered, the conductor temperature and the fiber temperature are higher than those without considering the twisting; meanwhile, with the increase of the pitch, the twisting angle becomes smaller, and the temperature decreases; under the same conductor temperature, the larger the pitch is, the lower the fiber temperature will be. The flow of seawater during laying has a significantly stronger heat dissipation effect on the cable than that when buried. The larger the convective heat transfer coefficient is, the lower the temperature of the conductor and optical fiber will be. Under the same conductor temperature, a larger conductor cross-sectional area leads to higher fiber optic temperatures.