In recent years, the research on power system black- start for the large-scaled break-off power fault is becoming an absorbing topic regarding the power system safety. The starting of induction motor machines that have large output power is a big threat to ensure the reliable running of a small system at the initial period of black-start. In this article, RTDS tool was utilized to simulate the black-start situation at the initial period that the small system was running at no load, and based on the obtained data, those issues, such as over-voltage and the capability of carrying power are studied. The factors that may induce system fault were analyzed, and in conclusion, the reactive power impact and trend of the real power changing should be the principal reason. Keywords-black-start; no-load; over-voltage; self-excitation; stability