Aiming at the problems of 10 kV outlet switches in substations and smart switches on distribution lines that the upper and lower protection fit always fails, the protection range extends to the next level or the protection has low sensitivity, a method based on system-related parameters which focuses on two-phase short-circuit fault type is proposed. Taking a typical single radiation line from Jiangxi Province as an example, the method of the protection fit in low load distribution lines and the setting calculation of switching at all levels is analyzed in detail. The results show that the method can effectively increase the protection range, optimize the switch fabric distribution, and ensure the protection selectivity while greatly simplifying the protection setting. Finally, the calculation software is designed based on the setting calculation method which can automatically set the calculation and verify the protection range according to the relevant parameters of the system. This work is supported by Science and Technology Project of State Grid Corporation of China (No. 52182017000V) and Science and Technology Project of State Grid Jiangxi Electric Power Company (No. 52182016001N).