The solid-state circuit breaker (SSCB) is a crucial component in the protection of DC distribution networks in that they facilitate reliable, arc-free, and fast isolation of DC faults. First, a novel medium-voltage DC SSCB topology based on cascaded silicon carbide (SiC) junction field effect transistors (JFETs) is proposed. When a DC fault occurs, metal oxide varistors (MOVs) are used to provide driving voltage to the gate-source terminals of cascaded normally-on SiC JFETs of the SSCB main switch. These can achieve fast DC fault protection. Additionally, the operational characteristics of the SSCB turn-off and turn-on processes are analyzed in detail, and the design method of key parameters of the SSCB drive circuit is proposed. Finally, a 1.5 kV/63 A medium-voltage SSCB prototype based on three cascaded normally-on SiC JFETs is developed, and the effectiveness of the design scheme is verified through short-circuit fault and fault recovery experiments. The results indicate that the response time for the SSCB to turn off the 250A short-circuit current is about 20 s. Fault recovery conduction response time is about 12 s. This provides a foundation for the topology optimization design of medium-voltage DC SSCB and the improvement of dynamic and static voltage balance performance of cascaded normally-on SiC JFETs.