The invention discloses a digital closed-loop test system for a stability control system. A RTDS (Real Time Digital Simulation System) comprises N pieces of parallel GTNET boards; a process layer switch is respectively connected with a security and stability control system and the N pieces of parallel GTNET boards through a cable; the GTNET boards transmit SV analog quantity and GOOSE switch quantity signals output by the RTDS to the security and stability control system through the process layer switch, wherein N is greater than 1; and GOOSE trip outlet signals output by the security and stability control system are transmitted to the GTNET boards of the RTDS through the process layer switch. According to the digital closed-loop test system for the stability control system provided by theinvention, the analog quantity and switch quantity acquisition and trip signal outlets of the stability control system are achieved through VLAN setting and a digital interface communication configuration file of a router, so that a complete digital closed-loop test system of the stability control system is formed; and full digitalization of input and output of the stability control test system is realized, and the efficiency and reliability of stability control policy verification can be improved.