The invention discloses a warning tape and a preparation method thereof, belonging to the technical field of industrial tapes. The warning tape comprises a transparent PVC film, a printing layer, a PVC base material, a bridging agent layer and a glue layer stacked from top to bottom. After adding the printing layer to the PVC base material layer, it is hot-pressed and bonded with the transparent PVC film; and by preparing glue, brushing the printing layer on the top of the PVC base material, and then heat-compressing and bonding the transparent PVC film, and applying it on the bottom of the PVC substrate A layer of bridging agent, followed by a layer of glue, aged, cooled, cut, and rolled into tape rolls to obtain the finished product. The warning tape prepared by the invention has excellent anti-shedding and delamination, high firmness, good aging resistance, good weather resistance, and the effect of preventing edge warping and fading, is reliable and durable, and is suitable for popularization and application.