Abstract: Polyethylene film warning tape has always been the main tool for the safety isolation measures of the secondary cabinet in the substation. However, due to its shortcomings, it has caused some problems and even accidents in the use process. In this paper, by investigating the shortcomings of traditional warning tapes and the needs of substation operators for warning tapes, and analyzing the technical means of existing telescopic warning tapes on the market, a more practical and safe telescopic warning tape is designed. The overall structure, technical principle, main performance and outstanding advantages are described in detail.