A new kind of micro-electro mechanical system (MEMS) current sensor based on po lymer material is proposed.The properties of this sensor′s key element polymer MEMS torsion micro-mirror are studied.This torsion micro-mirror has a composite structure,which is constructed by metal an d polymer materials.The substrate material of this sensor is polycarbonate (PC) and the to rsion beam is made of metal,permanent magnet is built into the base structure and packaged by poly mer material. One plane of the torsion micro mirror is designed to be a reflection grating.Th e working principle of this current sensor is given and the impacts of different feature p arameters of this torsion micro-mirror on torque and torsion angle are analyzed.The results show that th e torque is proportional to the current magnitude,and the torsion angle amplitude is also p roportional to the alternating current (AC) amplitude when the torsion micro-mirror is under stead y-state vibration. The torsion angle amplitude becomes larger when the torsion beam is longer,and the torsion angle amplitude decreases when the radius of torsion beam becomes larger.Accord ing to the detection and demodulation results of the zero-order diffraction light intensit y produced by reflection grating on torsion micro-mirror,the sensitivity of thi s MEMS current can reach 0.024/A.