The invention provides a same-tower double circuit line phase selection method. The method comprises steps that step (1), an electrical quantity of a single circuit line is utilized to calculate a positive sequence break variable voltage deltaU1, a negative sequence voltage U2 and a zero sequence voltage U0 when the negative sequence voltage U2 is not equal to zero; step (2), when the zero sequence voltage surpasses the negative sequence voltage, an angle theta1=arg(U0/U2) is calculated, when the positive sequence break variable voltage surpasses the negative sequence voltage, an angle theta2=arg(deltaU1/U2) is calculated; step (3), six-phase-region faults of double circuit line faults are determined according to relationships of sequence voltage amplitudes and relationships of sequence voltage phases at a protection mounting portion; step (4), a positive sequence break variable current deltaI1, a negative sequence current I2 and a zero sequence current I0 of double circuit lines are calculated; step (5), the six-phase-region faults of the double circuit line faults are further determined according to phase relationships of sequence currents and amplitude relationships of sequence currents at the protection mounting portion; and step (6), a fault of a present circuit line protection component is determined through utilizing a positive sequence break variable impedance deltaZ1 and a negative sequence impedance Z2 when the negative sequence voltage U2 is equal to zero.