Abstract: In view of the influence of conductor eccentricity on the all-fiber optic current transformers（FOCTs）,the corresponding distributed parameter model for the sensing coils of FOCTs is developed based on the distributed parameter model for sensor sections of optic current transformers.Based on the distributed parameter model of sensing coils,the influence mechanism of conductor eccentricity on FOCTs is proposed.The mechanism reveals the reasons for leading to the eccentricity problem of FOCT,i.e.,the combined effect of sensing fiber linear birefringence and nonuniform magnetic field on the sensing coil.The influence of measured conductor eccentricity on the measuring accuracy is analyzed.The conclusion that the eccentricity could only influence the ratio error of FOCT instead of linearity is obtained.The results of theoretical analysis are in agreement with experimental results,which shows the correctness of the theory and conclusion proposed.