The performance of passive Optical Current Transformer(OCT) with the linear birefringence is analyzed based on Jones matrix.The results show that passive OCT still works when the output light is circularly polarized,and the output voltage of passive OCT is affected by linear birefringence even though the output light is linearly polarized.The performance of passive OCT is analyzed when the Polarization angle and phase shift of the incident light and the different initial birefringence are introduced.The results show that when the initial birefringence exists,the relative deviation of system output has minimum.The corresponding incident light phase shift to minimum monotonically increases with the initial birefringence.A method of reducing the influence of passive OCT initial linear birefringence is proposed based on increasing the phase shift of incident light.The numerical and experimental results prove its feasibility.Developed practical optical current transformer has reference significance to improve the performance of passive OCT.