A phase shifter, a preparation method thereof, and a phased array antenna. The phase shifter includes a substrate (5); two ground lines (1) located on the substrate (5); a signal line (2) located on the substrate (5) and between two ground lines (1), wherein there is a spacing between the signal line (2) and the ground line (1); a dielectric layer (3) located at a side of the signal line (2) and the ground lines (1) away from the substrate (5); at least one bridge (8) located at a side of the dielectric layer (3) away from the substrate (5), projections of the ground lines (1) and the signal line (2) on the substrate (5) are overlapped with a projection of the bridge (8) on the substrate (5), and there is a spacing between the bridge (8) and the dielectric layer (3).