The invention relates to a method for preventing a distance protection misoperation caused by PT line breakage. Three phases of voltage amplitudes before and after a switch is closed are measured; when the conditions that an absolute value of a voltage value of any phase of voltage in the three phases of voltage before closing is less than a threshold value K, and the absolute value of a difference between the phase of voltage after closing and the phase of voltage before closing is also less than the threshold value K are simultaneously met, the PT line breakage is judged, wherein K is less than or equal to 0.1V and greater than or equal to 0.01V; and if the PT line breakage is judged, a blocking distance protection is carried out. According to the method, the problem of the distance protection misoperation in the PT line breakage is solved.