The invention relates to a method for preventing a misoperation caused by voltage loss after a starting distance protection of a power grid. The method comprises the steps as follows: continuous n sampling points meet the criteria as follows: (1) a voltage sudden change quantity of any phase is greater than a set voltage sudden change threshold value; (2) three phases of voltage calculated by a half-cycle algorithm are less than 2V; (3) three phases of current sudden change quantities within 20ms are greater than a start constant value of a distance protection device; (4) zero-sequence current or negative-sequence current is less than a set current threshold value; and (5) a line pilot main protection is not opened, wherein n is a positive integer; the condition that line breakage of a voltage transformer is generated within a time period after a positive external symmetrical fault is judged; and the misoperation of the distance protection device is prevented according to the judgment result. Through the method, whether the line breakage of the voltage transformer is successively generated or not within a short period of time can be judged when the distance protection device is started due to the positive external symmetrical fault and a present line in which the distance protection device is located is a short line, so that the misoperation of the distance protection is avoided; and the safety of the system is improved.