When a fault occurs on a DC microgrid line, the rapid surge of fault current is extremely detrimental to the reliability of the system power supply. Therefore, a quick fault detects and remove is important for the reliable operation of power supply. The traditional current differential protection has good quick rapidity and selectivity. However, its sensitivity is greatly affected by the short circuit impedance and may lead to the malfunction of protection under the high resistance short circuit fault. Aiming at the radial topology of DC micro-grids, according to the current variation characteristics at both sides of the fault point, a low braking coefficient is utilized to realize the detection of high resistance faults, and the protection scheme is simulated and verified by building a DC micro-grid model in PSCAD/EMTDC. The simulation results indicate that the improved protection scheme can accurately identify and remove the faults when different short-circuit impedance faults occur in the protected DC lines.