This　paper　analysed　the　trajectory　control　(TC)　based　on　natural　switching　surface　(NSS)　in　dual-active-bridge　(DAB)　DC-DC　converter.　Which　improves　the　fast　transition　process　when　load　changes　from　constant　resistor　(CR)　to　constant　power　(CP).　In　order　to　obtain　the　NSS　based　state　trajectory,　the　state-space　equation　is　derived　mathematically　based　on　the　small-signal　model　of　DAB　converter.　Under　the　TC,　the　DAB　can　both　achieve　the　constant　power　load　(CPL)　stability　and　fast　start-up　stage　simultaneously.　Finally,　the　comparison　of　open-loop　control,　closed-loop　with　linear　controller　and　TC　are　given　to　validate　the　effectiveness　of　the　proposed　strategy.　©　2020　IEEE.