The invention discloses a current differential protection method, device and system for grid-connection tie lines of a large-scale inverter type power supply based on a negative sequence component. The current differential protection method comprises the steps of S1, collecting current flowing through protection 1 and protection 2 at two ends of a tie line PQ, and calculating the corresponding current phasor; S2, respectively calculating a positive sequence component, a negative sequence component and a zero sequence component of the current phasor at two ends of the tie line; S3, respectivelycalculating synthesis current of the system side and the inverter type power supply side so as to give prominence to the negative sequence current difference of the two ends of the tie line; S4, calculating a differential ratio coefficient; S5, respectively calculating differential current Idiff.phi of phase lines in three phases; S6, setting a protection action threshold Krel and a segregated phase current differential protection set value Iset, and determining that there is a fault in the tie line area when one of the following conditions is met: the differential ratio coefficient Cdiff isless than or equal to the protection action threshold Kref, or the differential current Idiff.phi is greater than the segregated phase current differential protection set value Iset; and S7, if it isjudged that there is a fault in the tie line area, sending a trip signal by the protection so as to isolate the tie line fault area from the system. The current differential protection method can reliably differentiate faults inside or outside the area from the normal operation condition, and overcomes a problem of low sensitivity of the traditional current differential protection.