Networked　systems,　such　as　telecommunications,　transportation,　and　power　transmission,　are　critical　for　the　economic　development　and　social　well-being　of　a　society　and　are　required　to　keep　the　prescribed　demand　continuously　satisfied.　Therefore,　when　planning　maintenance　actions　for　such　a　system,　the　adverse　influence　on　its　reliability　caused　by　the　unavailability　of　the　components　in　the　process　of　being　maintained　needs　to　be　taken　into　account.　To　deal　with　this　problem,　we　propose　a　new　bi-objective　optimization　approach　to　determine　the　Pareto　optimal　maintenance　plans　for　a　networked　system,　simultaneously　maximizing　its　reliability　within　the　concerned　planning　horizon　and　minimizing　the　total　maintenance　cost.　Both　perfect　and　imperfect　maintenance　actions　are　considered.　The　proposed　approach　can　well　balance　the　influence　of　maintenance　actions　on　a　networked　system＇s　reliability　during　their　implementation　and　after　being　completed　and,　thus,　can　help　ensure　its　reliability　of　continuously　satisfying　the　prescribed　demand.