After the pole-to-pole short circuit fault of DC region distribution system, the power electronic converter needs to be quickly locked, which seriously affects the reliability of power supply and causes the difficulty of low-voltage area fault location. In this paper, a mechanism of no locking VSC converter and DC/DC current limiting after fault is proposed, to solve the problem of fault area location, the fault characteristics of pole-to-pole short circuit fault in low voltage area are studied. On this basis, the fault characteristics of pole-to-pole short circuit fault in low-voltage area are studied. The result shows that the shortcircuit current, voltage drop and fault development are obviously different in different voltage levels. Taking advantage of the difference between inside and outside fault zones, a fast fault region location method based on the difference of fault characteristics is proposed. The simulation model of DC regional distribution network is set up in the simulation software PSCAD, which verifies the feasibility of the fault location method proposed in this paper.