Abstract: A rotation speed measurement method based on a femtosecond optical frequency comb is provided. In the method, a rotation axis of a rotating object to be measured and an optical path main axis are coplanar, and perpendicular to each other, and a first converging lens focuses an emitting beam obtained by expanding the laser on a surface of the rotating object. A repetition frequency and a carrier-envelope offset frequency of the femtosecond optical frequency comb are locked during the measurement. A repetition frequency difference is read from a frequency counter. A rotation speed of the rotating object is calculated as follows: M = c ? ? ? f r 4 ? ? ? f r ? sin ? ? ? R = ? ? ? ? f r R .