Abstract: According to the actual situation of 500 kV submarine cables bundled with the special submarine optical cables in HainanNetworking System,combined with the IEC60287 thermal circuit model optimized by finite element simulation model,the temperaturedistribution of the submarine cable can be monitored by distributed optical fiber sensing technology. An onshore simulation experimentplatform is set up in the laboratory,and the medium-voltage cable bundled with optical fiber is used for onshore simulation experiment.At the same time,the verified temperature monitoring method is applied to the 500 kV submarine cable in Hainan Networking System.Based on the point at bare air section of the C-phase,the temperature change of the optical unit for bundled optical cable is tested. Thefinite element simulation is used to calculate the surface temperature of the cable,and then the corresponding conductor temperature isderived by using the thermal circuit model according to the temperature of the cable surface,thus obtaining the temperature change ofthe cable conductor during actual operation. The error between the conductor temperature measured by both the onshore simulationexperiment and numerical calculation is less than 1.77%,verifying the accuracy of the submarine cable conductor temperaturemonitoring method.