A method of designing a kind of shared aperture radar absorbing material (SA-RAM) is presented, in which method the scattering problem of passive metamaterial (MTM) is converted into the radiation problem of active array. Multifunctional SA-RAM is realized by optimizing the position, amplitude, and phase of the MTM subarray composed of finite MTM structures based on the array theory. An SA-RAM with absorber and phase cancellation characteristics is fulfilled by interleaving artificial magnetic conductor (AMC) subarray and perfect metamaterial absorber (PMA) subarray. Simulation and experimental results demonstrate that the backscattering radar cross section (RCS) of SA-RAM is smaller than that of the metal plate in a frequency range of 5.5-8.3 GHz. Especially, the RCS reduction is caused by high absorbance at 5.54 GHz and by phase cancellation between AMC subarray and PMA subarray at 7.0 GHz. The idea can help to design radar absorbing material, which combines frequency stealth with space stealth function.