Abstract: Although the single phase short fault normally has little impact on stability of the power system, its improper settlement will probably lead to loss of stability. According to the actual usage condition of single phase reclosure equipment and based on the characteristic curve of generators, the stability of power system in black start period is analyzed and simulated when the system is subjected to the single phase fault and the reclosure action happens soon afterwards. It is pointed out that the action of single phase reclosure may lead to instability results, and the precaution methods are suggested. It provides theoretical basis for the proper deploy the reclosure plan in the black start period. The validity and effectiveness of the conclusion is verified through real system simulation.