In this letter, a two-layer metasurface is proposed to achieve radar cross-section (RCS) reduction of a stacked patch antenna at a broadband. The lower layer metasurface is composed of four square patches loaded with four resistors, which is utilized to reduce RCS in the operation band (2.75-3.4 GHz) of the patch antenna. The periodic square loops with four resistors mounted on each side are adopted to construct the upper layer metasurface for absorbing the incoming wave out of band. We first investigate the effectiveness of the proposed metasurface on the RCS reduction of the single stacked patch and then apply this strategy to the 1 x 4 stacked patch array. The proposed low RCS stacked patch array antenna is fabricated and measured. The experimental results show that the designed metasurface makes the antenna RCS dramatically reduced in a broadband covering the operation band and out-of-band from 5.5-16 GHz. Moreover, the introduction of metasurface is demonstrated to have little influence on the antenna performance.