The　influence　of　the　picosecond　(ps)　pulsed　burst　with　a　nanosecond　scale　of　temporal　separation　(50　ns)　on　filamentary　traces　in　sapphire　substrate　is　investigated.　The　spatiotemporal　evolution　of　the　filamentary　plasma　string　induced　by　sub-pulses　of　the　burst-mode　is　revealed　according　to　the　analysis　of　the　instantaneous　photoluminescence　images.　Due　to　the　presence　of　residual　plasma,　the　energy　loss　of　sub-pulse　during　the　balancing　of　self-focusing　effect　is　reduced,　and　thus　refreshes　the　plasma　via　refocusing.　The　refreshed　plasma　peak　generated　by　the　subsequent　subpulse　appears　at　relatively　low　density　positions　in　the　formed　filamentary　plasma　string,　which　results　in　more　uniform　densities　and　less　spatial　overlap　among　the　plasma　peaks.　The　continuity　and　uniformity　of　the　filamentary　trace　in　sapphire　are　enhanced　by　the　burst-mode.　Besides,　the　burst　filamentary　propagation　can　also　remain　effective　when　the　sub-pulse　energy　is　below　the　self-focusing　threshold.　Based　on　this　uniform　and　precise　energy　propagation　mode,　the　feasibility　of　its　use　for　the　laser　lift-off　(LLO)　process　is　verified.