In active distribution networks，the uncertainty of a large number of distributed energy resources increasingly accentuates voltage stability issues.Existing optimization methods typically treat the economic efficiency and voltage stability of distribution networks independently，seldom considering their interconnection，which hampers the efficient utilization of flexible resources.An interlayer connection factor is introduced，and a bi-layer voltage optimization model for distribution networks based on the Sobol ’s method is proposed.Firstly，a probabilistic load flow calculation model in active distribution networks that considers distributed energy resources in the networks and the load uncertainty is constructed，and the impact of load fluctuations on the L-index is quantitatively analyzed through global sensitivity analysis using the Sobol ’s method.Subsequently，based on the results of the sensitivity analysis，the interlayer connection factors are calculated，and these factors are used to link the upper-layer economic objectives with the lower-level stability objectives to establish a bi-layer optimization model.This model optimizes the flexible resources in the system.Finally， simulations are conducted on a modified IEEE 33-node system using the proposed optimization model.The comparison verifies that the proposed model can improve the optimization efficiency and support the economic and safe operation of distribution networks.