Doublelayer diffractive optical elements (DOEs) can work within a wide spectral band and have high diffraction efficiency. A mathematical analytic model of the polychromatic bandwidth integration average diffraction efficiency for doublelayer DOEs in a certain incident angle range is proposed. A 0.4 to 0.9 μm wide waveband optical system containing doublelayer DOEs is designed. The optical system has a focal length of 28 mm, a F/# of 2 and a field of view of 18°. It uses a Petzval objective structure consisting of four lenses. Its Modulation Transfer Function (MTF) is greater than 0.67 at 60 lp/mm. The bandwidth integration average diffraction efficiency of its doublelayer DOEs is above 91% in the 0.4 to 0.9 μm waveband. In the optical system, the incident angle upon the diffractive surface is within the range of 0° to 8.62°. The comprehensive bandwidth integration average diffraction efficiency of the double-layer DOEs is 97.36%. Compared with the traditional refractive wide waveband optical system, this wide waveband optical system containing double-layer DOEs has a simpler structure and higher resolution.