Inversion of Rayleigh waves is studied for the first time by using the genetic algorithm based on the intensities of the fundamental and/or higher modes. The relations of all modes to the medium structure are investigated. It is emphasized that the higher modes and mode jumping should be considered in the inversion when the low-velocity layers are contained in the stratified half space. Shear wave velocity and thickness of each layer are inverted by the genetic algorithm. Compared with the least square method, the genetic algorithm has several advantages.It usually does not depend on the initial models and the global optimal solutions can be obtained easily. The influences of some parameters on the inversion are also analysed and some useful results are presented.