Abstract: Offshore wind power is developing towards the application scenario of long-distance and large-capacity clustered use. Researching safe, reliable, and economical offshore wind power transmission technologies is significant. First, this paper analyzes the influence of offshore reactive power compensation degree and system frequency on transmission capacity, and the analytical expression of system transmission capacity is obtained. Secondly, a full life-cycle cost model for High Voltage Alternating Current (HVAC), High Voltage Direct Current (HVDC), and Low-Frequency Alternating Current(LFAC) transmission systems was developed, considering the impact of factors such as frequency and reactive power compensation on equipment costs. With the system cost minimization as the optimization objective function, based on the boundary conditions of the offshore wind power transmission scenario in the deep sea, the system's optimal frequency and reactive power compensation distribution are solved. Finally, based on the optimal system cost of the three transmission methods, the full-capacity technical and economic range of offshore wind power transmission using different schemes is obtained. The results show that the transmission capacity is within the range of 300-2100MW, and the upper bound of the economic distance of the HVAC scheme is approximately 60-80km, while the upper bound of the LFAC is 150-210km. The results prove the technical and economic advantages of flexible low-frequency transmission technology in mid-to-long-distance, large-scale offshore wind power scenarios..