The　switching　rule　with　mode-dependent　average　time　(MDADT)　for　DC-DC　Buck　converter　are　mainly　designed　in　this　paper.　The　traditional　switching　rule　doesn＇t　consider　the　use　of　slow　switching.　In　terms　of　control　theory,　the　slow　switching　mode　can　also　make　the　systems　stable　because　the　switching　signal　combined　with　MDADT　keep　the　system　stable　asymptotically.　Moreover,　the　chattering　problem　of　sliding　mode　can　be　suppressed.　Performance　of　the　system　is　evaluated　according　to　a　series　of　simulations.　©　2019　IEEE.