Several methods utilized in designing microwave photonic phase shifter in the phased array antenna are compared and analyzed, the theory of the fiber vector sum microwave photonic phase shifter is investigated, and the structure of the phase shifter is designed. Variable directional coupler and polarization-maintaining fiber are used in the structure, which can reduce the complexity of the phase shifter and the coherent interference loss, thus enhancing the controllable performance of the phase shifter. The accuracy control of the fiber is analyzed and the scheme contains four polarization-maintaining fiber is given to achieve the phase shift of . The experiment with this phase shifter scheme is made, and the result shows that the scheme is practical and feasible.