Abstract: In order to compare and analyze transmission capability and economy of low-frequency transmission system and power frequency transmission system,electromagnetic,thermal and current coupling simulation model was established by COMSOL,current carrying capacity of power frequency and low frequency offshore wind power transmission system was analyzed,and equipment cost and loss cost in system were calculated,so as to make economic comparison between power frequency and low-frequency transmission.Results showed that when voltage level,cable section and cable laying parameters remained unchanged,submarine cable phase loss,sheath loss and armor loss all decreased to varying degrees with decrease of load frequency,and the decreasing trend was more obvious with gradual increase of load current.Compared with power frequency transmission,the cross section of submarine cable conductor could be reduced by 1-3 grades according to different transmission conditions.When low-frequency transmission was used,the smaller cross section led to increase of internal phase loss of submarine cable,but sheath loss and armor loss were reduced,and total loss was lower than that of power frequency transmission with the same capacity.When capacity of offshore wind farm was 600 MW,transmission line adopted 220 kV submarine cable,and when transmission distance increased to 32 km,the economic advantages of flexible low-frequency transmission technology began to appear.Results could provide data support for future new power transmission system.