Based on the general theory of the optical transformation, a new method for designing diffractive phase elements generating multi-focal annuli is presented. The number and the position of focal annuli, as well as the width of focal annuli may be predetermined arbitrarily according to the particular demands. Several simulation designs are carried out for the Gaus-sian-profile laser illumination. We also investigate the influence of phase quantization on the results of designs. The simulation calculations show that the new method can be successfully applied to the designs of the desired diffractive phase elements for generating multi-focal annuli.