The sediments moving on-off shore in wave field on lake-sea submarine slope are coupled by wave and gravity field. The net on-off shore displacement of the sediments leads to the changing of submarine morphological profile in slope and the gradient of slope. This is a morphological response process to external agent. The condition of coupling equilibrium profile is:ΔS₁=ΔS₂cosβ=0 ΔS₃=±[(S₄⁺-S₅^-)²-4S₆(S₇⁺-S₈^-)sinα+4S₆²]^1/2 β=arctg[tga-2S_q/(S_a⁺-S_a^-)cosα] There is an approximate relation between gradient of the slope in equilibrium (θe) and asymmetrical gradient of the oscQlating motion of sediments along the submaxine shore slope. ?θe/?x=?(S_a⁺-S_a^-)/?x·R where, S_a——net displacement of sediment in a period of wave; S_ax——net displacement of sediment in a period of wave in the direction perpendicular to shoreline; β——angle between displacement vector of sediment and the shoreline in a period of wave; α——angle between incident wave and shoreline;S_q——distance of sediments displacement caused by the gravity along the slope in half period of wave; S_a⁺——distance of onshore displacement of sediment caused by wave; S_a^-——distance of offshore displacement of sediment caused by wave; R——coefficient (> 0)