Abstract: Greenhouse single-layer spherical latticed shells (SLSLSs) offer advantages such as high load-transfer efficiency, large covered space, and excellent light transmittance, leading to their increasing application in agricultural greenhouse structures like botanical gardens, ecological parks, and sightseeing parks. However, as the span increases, their insufficient out-of-plane stiffness becomes increasingly prominent, which can easily lead to functional impairment and instability failure. To address the aforementioned issue, this study, based on the fundamental concepts of thin-shell stability theory and member stability theory and incorporating the results of multi-variable nonlinear stability analysis of the Williams double-rod structure, four node well-formation equations were proposed as the theoretical basis for cable-laying. Additionally, a unified cable-laying method applicable to SLSLSs was established in this study. This proposed method primarily involved the following steps: First, the well-formation of nodes along the radial direction of SLSLSs was calculated according to the node well-formation equation. Second, since the node well-formation equation served as an important quantitative measure of node stiffness, the node position with the smallest well-formation could be identified through comparison. Then, a standard strut with a length ratio of 1 was installed at this position, while the strut lengths at other radial nodes were set based on their relative well-formation ratios. Finally, cross-cables were arranged to form, together with the struts, a cable-supported system possessing high in-plane stiffness, thereby providing effective out-of-plane stiffness enhancement for SLSLSs. By adjusting three parameters including the rise-span ratios (1/8, 1/7, 1/6, and 1/5), sag-span ratios (1/25, 1/20, 1/18, and 1/15), and cable-laying methods of greenhouse SLSLSs, various forms of cable-supported greenhouse SLSLSs could be constructed based on the cable-laying method proposed in this paper. The research employed the large-scale finite element (FE) analysis software ANSYS and a self-developed APDL program for numerical simulation analysis. Refined FE models of greenhouse SLSLSs with cable-free and cable-supported were established. The Beam188 element from the element library, which considers large deformations and shear deformations, was used to simulate the members of SLSLSs, while the Link10 element was used to simulate the tension-only flexible cables and compression-only rigid struts in the cable-supported system. Elastoplastic static stability analysis and parametric studies were conducted. The effects of different cable-laying methods, rise-span ratios, and sag-span ratios on the stability capacity of cable-supported greenhouse SLSLSs were comparatively analyzed. The results indicated that: (1) under four different rise-span ratios, compared to cable-free greenhouse SLSLSs, the stability capacity of cable-supported greenhouse SLSLSs showed a significant improvement, with an increase ranging from 24.4% to 57.8%. The primary reason is that cable-free greenhouse SLSLSs under different rise-span ratios all exhibit deformation characterized by prominent central top protrusion and mid-circumferential depression, while the cable-laying method based on node well-formation effectively enhanced the local stiffness of the central top and mid-circumferential regions of SLSLSs. (2) For different sag-span ratios and cable-laying methods, compared to cable-free greenhouse SLSLSs, the maximum improvement in the stability capacity of cable-supported greenhouse SLSLSs with rise-span ratios of 1/8, 1/7, 1/6, and 1/5 was 57.8%, 56.3%, 46.5%, and 38.1%, respectively, among which the rise-span ratio of 1/8 yielded the greatest improvement. (3) For different rise-span ratios and cable-laying methods, compared to cable-free greenhouse SLSLSs, the maximum improvement in the stability capacity of cable-supported greenhouse SLSLSs with sag-span ratios of 1/25, 1/20, 1/18, and 1/15 was 33.9%, 31.2%, 36.7%, and 38.1%, respectively, among which the sag-span ratio of 1/15 yielded the greatest improvement, and the cable-laying method based on node well-formation Equation (2) provided the greatest increase in stability capacity. The cable-laying method proposed in this study and the conclusions drawn hold theoretical significance and reference value for the performance enhancement, stability design, and engineering practice of large-span cable-supported greenhouse SLSLSs.