The invention discloses a grounding detection system and method of an alternating-current charging control device. The system comprises a charging and discharging unit, a comparison unit, and a detection unit. The charging and discharging unit includes a charging and discharging device; the charging and discharging device, an equivalent resistor of a load of a charging and discharging circuit inside an alternating-current charging control device, a ground wire of the alternating-current charging control device, and a charging circuit of a constant flow source inside the alternating-current charging control device are connected in parallel to form an RC charging and discharging circuit; and a terminal voltage of the charging and discharging device is used as a detection voltage. The comparison unit is used for comparing the detection voltage with a preset reference voltage; when the output voltage is higher than the preset reference voltage, a starting signal is outputted to the detection unit. The detection unit determines whether grounding of the alternating-current charging control device is normal according to discharging time.