An electrically tunable metasurface is designed for radar cross-section (RCS) reduction application in this paper. It consists of 24 × 24 cells individually loaded with variable capacitors so that their phase profiles can be independently controlled by the bias voltage. Therefore, based on the diffusive scattering principle and reflect-array theory, we arrange the adaptive phase differences between adjacent basic elements and reconfigure the appropriate phase distribution determined by a genetic algorithm (GA) corresponding to the operation frequency. Thus, stable monostatic and bistatic RCS reduction with normal incidence can be realized over a wide band by independently tuning the capacitance of each loaded varactor. Simulation results verify that the bistatic RCS reduction can reach at least 10 dBSm within both 4.2-7.3 GHz and 9.3-11.3 GHz. Simultaneously, the monostatic RCS reduction reaches at least 17.5 dBSm and 14 dBSm within the above two bands, respectively. INDEX TERMS Metasurface, radar cross section, varactor tuning.