Abstract: It is important to be able to characterize magnetic materials under the effect of a rotating field and to specify the influence of anisotropy. In this goal, different methods are used classically. In this study we describe the main features of a novel set-up for the determination of rotational hysteresis power losses in soft magnetic materials. The flux search coil has 2 windings wound along diagonal lines of a square insulator into which the specimen is inserted, addition and subtraction of two output voltages from these winding give the signals proportional to the flux change rate in the direction parallel and transverse to the longitudinal direction of the ribbon therefore, two values of loss corresponding to two magnetizing directions are obtained using a numeric acquisition and measurement result treatments. A non oriented 3.5% Silicon-Iron power loss measurements in a very large induction range, are reported.