Abstract: To apply the constant-accel-potential and stepping-accel-potential methods for extending the lifetime of gridded ion thruster,the uncertainty in the electron backstreaming limit(V_EBS) of LIPS-200 is quantified based on QMU and WGW methods.The results show that this uncertainty arises from the uncertainty in each of the correlated parameters,which include plume electron temperature,accel grid aperture size,beamlet diameter,beamlet current,accel grid thick-ness,grid gap,and plume plasma potential.Currently,the best estimation and upper bound of the uncertainty in VEBS are 7.4 V and 17.6 V,respectively.Through an uncertainty control on main parameters,these values can be reduced to 5.1 V and 13.0 V,respectively.By reducing the uncertainty in V_EBSfrom 15 V to 10 V,the optimized thruster lifetime can in-crease by 570~885 h.