The applicability of the open-end spinning system for wool is investigated by the rotor type open-end spinning system having a revolving separator which is a different one from the existing device. The effects of the revolution of the separator on the fiber configuration in the fleece accumulating on the collecting surface of the rotor, the yarn evenness and the fiber configuration in the yarn were studied experimentally. The ratio of the r.p.m. of the separator to that of the rotor influences upon the yarn evenness. Most of the yarn are bent or irregularly curved and about 10% of fibers in the yarn have a normal helical form. The experimental results are discussed assuming that the rotor and the revolving separator are vertical coaxial cylinders and the annular air flow between them are tangential laminar flow of an incompressible fluid.