The phase consistency of mm wave band network is affected by processing accuracy, roughness of copper foil and inconsistent thickness of sheet, resulting in phase difference in the cable output port of iso phase design, and the traditional phase adjustment method increases circuit complexity, which is high cost and not convenient for late adjustment. In this paper, a method of precisely adjusting phase by rectangular defected ground structure(DGS) is proposed, modeling simulation analysis and parameter scanning are carried out by electromagnetic simulation software, and the results show that the load-rectangular defected ground structure of the ribbon port voltage stop wave ratio is less than 1.3 insertion loss is less than 0.7dB, at 30 to 34GHz, two rectangular defected ground structures are used to precisely adjust the phase of the two transmission lines with a phase difference of 14.5 degrees to the phase difference of less than 0.1 degrees, and the structure can adjust the different phases precisely according to the actual processing results, simplify the circuit structure and reduce costs.