Abstract: The uncertainties in form finding of tension structures were considered. Factors in form finding models can be treated as random variables reflecting inherent uncertainties. The special cable element method for form finding of specified prestressed cable net was used. The partial derivatives were derived for the equivalent external force vector, equivalent internal resisting force vector and tangent stiffness matrix. The sensitivity iterative formulas of initial balance shape coordinates were presented. With the sensitivities of shape coordinates and the sensitivities of cable length in balance state, the sensitivities of unprestressed cable length were calculated, and the sensitivity of the unprestressed cable length homogeneity was calculated. According to these sensitivity information, the design parameters of the cable network were modified, so that the unprestressed cable length is more homogeneous and the construction is more convenient. The process can also be applied to form finding of specified unprestressed-cable-length net to homogenize the prestress distribution in order to improve the network capability under stress.