Abstract: Communication cables with B1 class combustion performance, especially halogen-free unshielded digital communication symmetrical cables, is difficult to meet the requirements of B1 class combustion performance.Because LSZH sheathing material contains a certain amount of flammable polyolefin, flame retardancy of which is much worse than that of halogenated materials. In order to meet the design requirements of Class B1 halogen-free combustion characteristics for communication cables in GB 51348—2019, research was conducted on the structural design, key process control and other aspects of low smoke and halogen-free unshielded category 6 digital communication symmetrical cables, under the premise of meeting the attenuation transmission performance of the cable by reducing the proportion of ordinary polyethylene materials, and adopting materials with high flame retardancy, halogen-free sheathing and their processing technology. The cable with B1 class combustion performance was verified. Results showed that the carbonization height, combustion growth index and other indicators could meet the requirements specified in GB 31247—2014 standard.