Abstract: Using rectangular waveguide structure, and optimizing main parameters which affect the saturated differential phase-shift, a twin-toroidal ferrite phase shifter which can work from 12 to 18GHz is simulated. The bandwidth is up to 40%. The frequency dispersion is about 7. 8 while the amount of saturated differential phase-shift is about 370 . The insertion loss is better than 0. 4dB. At least three high-order modes exist, however they are not excited in the band. Matching the phase shifter to the waveguide whose width is 15. 8mm by two-step transformers. The return loss is less than -20dB. Simulation shows that wide-band characters may be improved by adjusting the permittivity of the transformer dielectrics and adding a capacitive step. A sample phase shifter is manufactured according to the design. Results of test indicate that the saturated differential phase-shift is about 360 , the frequency dispersion is about 8 and no peaks of insertion loss appear in the band.The insertion loss is better than 0. 6dB and the VSWR is less than 1. 4 in 12-17. 5GHz.