Abstract: Accurate calculation of dynamic temperature field and short-time allowable ampacity of submarine cables is of great significance to ensure safe operation of submarine cables. Aiming at the problem that the existing analytical methods can not accurately solve the dynamic temperature field and short-time allowable ampacity of submarine cables, an optimal thermal route analytical model is proposed. Building layered model of the cable body and the buried environment, deducing a set of formulas to calculate the equivalent thermal resistance and heat capacity of the external environment of the cable. Then the thermal path analytical model of the cable body and the environment is established by using thermoelectric analogy method. The optimal number of layers and optimal heat transfer radius of thermal path analytical model was selected by using control variable method. Finally, a 500 kV alternating current submarine cable is taken as an example to analyze and verify the proposed optimal thermal route analytical model, and the results show that model has good accuracy and high efficiency. The short-time amperage of submarine cable is evaluated based on the model, which shows that the short-time allowable maximum ampacity of submarine cable is related to the initial steady current and overload time of submarine cable.