The invention provides a start protection method applicable to a start process all region of a phase modifier transformer set. A dead region fault caused when a fault point occurs in a dead region between a grid-connected circuit breaker and a grid-connected current transformer is solved by source main transformer start current quick breaking protection of the phase modifier transformer set; the current in the main transformer start current quick breaking protection is from a main transformer low voltage side current transformer or a phase modifier machine end current transformer; the input condition of main transformer start current quick breaking protection takes voltage, frequency, current and auxiliary connecting point information of the grid-connected circuit breaker as the input basis; and the quit condition of main transformer start current quick breaking protection takes voltage and auxiliary connecting point information of the grid-connected circuit breaker as the quit basis,so that it is endured that the main transformer start current quick breaking protection does not occur error action when the position of the grid-connected circuit breaker is not reliable.