Spiral transition-metal dichalcogenides with broken crystal inversion symmetry and significant second-order nonlinear responses have shown great promise for further nonlinear optical applications. However, various spiral structures will be formed during their synthesis process, their second harmonic generation (SHG) varying with the layer thickness and which of them manifesting the most promising SHG response are still unresolved. Here, the layer-dependent SHG response is investigated for four representative spiral WS