A magnetic torsion micro-mirror optical current transformer with a composite structure is studied in this paper,which adopts data processing technology of n ormalized intensity. Good linearity of the sensor response is obtained,because the effects of the en vironmental change,light source fluctuation,and other factors on the intensity-modulated optical sensor can be eliminated.Design theory and sensing principle of the optical current tr ansformer are introduced,and the structural parameters of the sensing part are designed.We obtain the appropriate value of distance between collimator end and micro mirror through the simulation curves of coupling efficiency and micro-mirror torsion angle. The detection of current to optical intensity is realized by using the dual-fiber collimator.After optical signal processing,the experiment al results on the 50Hz alternating current test show that the response sensitivity maintains 0.034/A in the range of 5-50A,when the intensity of the light source is decrea sed by 3dB or the optical fiber attenuator is changed in the case of 3dB. The output response nonli nearity error is within±1%,and a good output response linearity can be achieved.