The injection and extraction deflectors of CSR are made of wrought
aluminium with surface anodic oxidation. From the results of MAFIA calculation, the fillet radius and the width of the high voltage electrode are set to 20mm and 60mm respectively, in order to have enough homogeneous electric field region and to improve its withstand voltage. Half of the cutting electrode is a set of tungsten filaments which has a diameter of 0.1mm, and the other half is beaten tantalum. A deflector model was built and tested under the simulated running condition. The experimental result is in accord with theoretical analysis.