• The current sensor with a NCF with bent-melt taper structure is proposed. As far as I am concerned, it is proposed for the first time. • The current sensor with bent-melt taper NCF shows high sensitivity, good repeatability and reversibility. • The average wavelength sensitivity is 10.48 nm/A and total relative transmission loss sensitivity is 17.28 dB/A. The sensitivities are higher than other sensors with the SMS structure. An all fiber current sensor based on magnetic fluid (MF) is proposed. The sensing structure is composed of a piece of no-core fiber (NCF) spliced between two sections of single mode fiber. The MF is used as the cladding of NCF. The sensing principle is based on the cladding mode interference. In order to improve the sensitivity, a bent-melt taper NCF is proposed as the sensing probe for the first time to increase the evanescent field. As a comparison, the sensitivities of optical fiber current sensors with straight NCF, bent NCF, and bent-melt taper NCF are measured in this paper. According to the experimental results, the sensitivities of optical fiber current sensor with bent-melt taper NCF are the highest among the three. The average wavelength sensitivity is 10.48 nm/A with the corresponding measurement range of 0–0.8 A, and the maximum standard deviation is 0.27 nm. The average total relative transmission loss sensitivity is 17.28 dB/A with the corresponding measurement range of 0–0.6 A, and the standard deviation of the maximum loss is 0.31 dB. The proposed sensor has good repeatability, reversibility and high sensitivity. [ABSTRACT FROM AUTHOR]