The invention relates to a processing method and system of a voltage dip. The method comprises steps of acquiring a system reference value of a voltage dip event according to data of multiple historyvoltage dip events and calculating a second probability value of an electrical appliance fault caused by the system reference value; according to a first estimation index value of the current voltagedip even, calculating a first probability value of an electrical appliance fault caused by the first estimation index value; according to the second probability value, correcting the system referencevalue, and according to the first probability value, correcting the first estimation index value; according to the corrected system reference value and the corrected estimation index value, judging the grade of the current voltage dip event; and according to the grade, selecting a corresponding preset measure to adjust a power supply device. According to the invention, the effect degree on the electrical appliance and effects on the index value caused by the voltage dip are fully considered; the serious degree of the voltage dip can be quite correctly judged; the corresponding preset measure can be adopted for adjusting the power supply device; and effects caused by the voltage dip are reduced and eliminated.