An exemplary method for controlling a charging current is adapted to a charging device. The charging device receives an input voltage to thereby output the charging current. The method includes the following steps of: making the charging current have a first value; judging whether the input voltage is less than a preset reference voltage; and if the input voltage is judged to be less than the preset reference voltage, decreasing the charging current from the first value step by step until the input voltage retrieves back above the preset reference voltage.