The invention relates to the millimeter wave wireless communication technology, and in particular to a double ground slot parallel micro-strip line 90-degree phase shifter which adopts a process 130nm SiGe BiCMOS. The double ground slot parallel micro-strip line 90-degree phase shifter includes a ground metal layer, a top metal layer, an input port, an output port, a dielectric layer and a substrate layer. An underlying metal transmission line is disposed at the center of the ground metal layer, and a parallel symmetric top metal transmission line is disposed on the top metal layer. A 180-degree phase inverter is disposed at the center of the underlying metal transmission line and the top metal transmission line. Two parallel symmetric trenches are disposed in the ground metal layer by taking the centerline of the underlying metal transmission line as the axis. The input port is connected with left ends of the top metal transmission line and the underlying metal transmission line. The output port is connected with right ends of the top metal transmission line and the underlying metal transmission line. The dielectric layer surrounds the bottom and the periphery of the ground metal layer and the top metal layer. The substrate layer is disposed at the bottom of the dielectric layer. The phase shifter improves the signal bandwidth, reduces the circuit area and phase error, and reduces the signal loss.