The invention discloses an optical fiber mutual inductor current measuring method based on reflective intensity modulation. The method comprises the steps of: firstly, establishing a mapping relation between a reflection coefficient and the distance from a reflection surface to an optical fiber end surface; secondly, measuring the reflection coefficient after the reflection surface is powered on, and calculating the distance from the reflection surface to the optical fiber end surface; then calculating the moving acceleration of the reflection surface, and further calculating the Ampere force applied to the reflection surface; and finally, based on the mass, the length, the Ampere force and the like, calculating the value of a tested current. According to the invention, the working principle of the reflective intensity modulation mutual inductor is utilized, and based on the phenomenon that a powered-on conductor generates vibration deviation under the effect of the Ampere force, the current is stably, accurately and safely measured; in addition, the measuring principle is reliable, the measuring result is high in precision, the realization cost is relatively low, the intelligent level of primary equipment in a transformer substation is improved, the operation stability of the transformer substation is improved, and the construction cost is lowered.