Wideband decoupling approaches for co-polarized metasurface arrays with ultrahigh-density arrangement are developed. The metasurface element is in the 2×2 chessboard configuration to ensure a compact size. Without introducing any additional layers and while preserving the compact layout of the entire metasurface array, effective approaches are proposed, making use of polarization orthogonality and current cancellation for wideband decoupling in the E-plane array, as well as odd-even mode cancellation for wideband decoupling in the H-plane array. To validate the efficacy of these wideband decoupling strategies, prototypes of decoupled two-element E- and H-plane metasurface arrays, as well as a 2×2 metasurface array, were fabricated and measured. Experimental results demonstrate that, with a profile as low as 0.032λ, both E-plane and H-plane arrays well achieve a wide decoupling bandwidth of 15.7% while maintaining an isolation level exceeding 20 dB. Meanwhile, a wide bandwidth of 12.1% is achieved for the 2×2 decoupled metasurface array.