We propose a novel fiber current sensor based on single light path detection and fiber loop scheme in order to solve the problem of low current sensitivity of traditional single light path detection fiber current sensors. Fiber loop scheme of this fiber current sensor is built by single-polarization single-mode couplers, which replaces the polarizer and the analyzer in traditional single light path detection fiber current sensors. This design not only keeps the advantages of simple structure and low cost, but also improves the current sensitivity of fiber current sensor via repeated cycle amplification, which inherits from the loop scheme. Both theory and experiment show that the system current sensitivity increases with cycle number K and the new fiber current sensor is feasible.