Two anti-interference structures of sensing fibers with variable pitch parts in fiber optic current sensors are proposed. One is fundamental structure, where the variable pitch part is bunched with the sensor fiber and the reflector is placed in the midpoint of the variable pitch part. The other is "8"-shape anti-interference structure, where the variable pitch part is wound into an "8" shape. The anti-interference principles of the two structures are analyzed. The differences of sensor readings are tested when the current conductor is at different points inside and outside the sensor fiber coil. The experimental results show that the external 1000 A level current disturbance can be resisted away from 0.5 m for both structures. However, the former only is applied to the applications where the relative positions of the current conductor and the sensor fiber coil are unchanged, while the latter can be applied to the many applications where the relative positions of the current conductor and the sensor fiber coil are not fixed. The anti-interference performances of both structures under different applications are practicable.