In this paper, a polarization modulated metasurface to improve the magnitude and expand the bandwidth of radar cross section (RCS) reduction is presented. Two physical mechanisms are responsible for the reflection diffusion of the proposed metasurface. One is the functionality of controlling the spatial distribution of polarization response, and the other is the capability of spanning the entire 2π phase range by making full use of the variable sizes and height difference of unit cells to achieve superwideband phase cancellation. A 10 dB monostatic RCS reduction is obtained from 3.87 to 92.89 GHz (a ratio bandwidth of 24:1) for both polarizations under normal incidence by simulation, which is identical to experimental results and theoretical analysis. The proposed method for suppressing vector fields in an extremely wide band may hold promising potentials for suppression of acoustic, electromagnetic, optical and other elastic waves.