Abstract: To address the issue of reduced voltage stability in weak areas caused by single-objective reactive power optimization, this paper derives the formulation of the L_u.p voltage stability index and incorporates it into the objective function of the reactive power optimization model. A multi-objective reactive power optimization method based on the L_u.p index is then proposed. Simulations are performed on the actual power grid of Hami, Xinjiang. The results demonstrate that the proposed multi-objective model effectively increases the voltage stability margin and improves the voltage stability of weak areas.