The utility model discloses a phaser used for an electric-modulating antenna. The phaser includes a fixed circuit board (16), a slidable circuit board (19), a pressing mechanism (17) and a metal shell (18); the slidable circuit board (19) is closely stuck on the fixed circuit board (16) to form a coupled microstrip line structure; the pressing mechanism (17) presses the slidable circuit board (19) on the fixed circuit board (16) to drive the slidable circuit board (19) to slide together for changing the electric length of the microstrip line to form a needed phase position change. When in use, one phaser is connected with two groups of radiation units at one end of the antenna and the other phaser is connected with two groups of radiation units at one end of the antenna; the two phasers and a zero-phase shift radiation unit in the middle of the antenna are connected by a power distributing circuit dividing one into three for forming five groups of phase shift units. The phaser used for an electric-modulating antenna has the advantages of small size, large phase shift amount and low loss. The phase position demand of declining by 12 degrees of an antenna of 2.5m can be met in a bandwidth of 806 to 960m to the most.