Subwavelength diffractive microlenses are analyzed by use of body-of- revolutionary finite-difference time-domain method. The electric field distributions on the focal plane of the element and the distributions from near field to far field are shown. The dispersion property of subwavelength diffractive microlens is investigated. The dispersion curve in the case of incident wavelength different from the design wavelength is shown. Numerical result illustrates the negative dispersion characteristic of the element, and the increase of focal length is faster than the decrease of incident wavelength.