Automatic Train Supervision (ATS) is an important component of the metro signal system, which can be coordinated with other subsystems in the signal system to realize the automatic signal management and automatic traffic scheduling monitoring of urban high-density rail transit. Taking the ATS system of Nanjing Metro Line 2 as an example, combined with the structure and working principle of the ATS system, the common fault handling methods of the ATS system are summarized. Through the analysis of the fault phenomenon and the description of the handling process, the maintenance quality of the ATS system is improved.