The study of plane pure-phase equi-width ring diffractive optical lenses is reported. The analysis and design methods of two-dimensional imaging double wavelength co-focus diffractive optical lens are also presented. The light intensity distributions show that it is a new type of ideal focusing optical element. Two light beams at 1. 06 μm and 0. 6328 μm can be focused on same focal plane by using this optical element. It may be used for focalization and alignment of invisible beam lasers such as 1.06 μm and 10.6 μm.