An in-situ SEM (scanning electron microscope) micro-torsion tester with high resolution is developed based on electromagnetism. The torque is controlled and measured using a coil-magnet component. The torsion angle is measured by a non-contact transducer based on Hall-effect. The calibration results show that the torque capacity of this tester is 1.6 x 10(-4) Nm with resolution of 1 x 10(-9) Nm. In-situ torsion test of MG (metallic glass) wire (Pd40Cu30Ni10P20) with a diameter of 111 mu m and a length of 3 mm is performed using this tester in SEM. A linear torque-torsion angle curve is obtained and the calculated shear modulus of the sample is 24.7 GPa. Meanwhile, the deformation process of the sample is simultaneously observed using SEM. It is the first time that the measurement of shear stress-strain and high resolution morphology observation are carried out simultaneously. (C) 2019 Elsevier Ltd. All rights reserved.