The compensation of negative-dispersion mirrors has very high request on design and preparation. The refractive index and physical thickness are the necessary parameters for the realization of the capability. Negative-dispersion mirrors are designed and prepared, which are analyzed from the main factors such as material refractive index, thickness, the sensitive layers and interface roughness considering the electric field distribution and the measurement result of group delay dispersion (GDD) and the scanning electron microscope. The research indicates: the refractive index in the design should be calculated from the experiment; increasing the thickness of total film and the cavity introduces the higher GDD; the electric field distribution decides the position of the sensitive layers; the thinnest layer may not be the most sensitive layer; the sensitive layers request high deposition accuracy ; interface roughness and inhomogeneity are both the important factors.