Abstract: Theory of the fiber vector-sum microwave photonic phase shifter was investigated, and the new-type structure of the phase shifter was designed. Variable directional coupler and polarization-maintaining fiber were used in the structure, which could reduce the complex and the coherent interference, the precision requirement of the fiber length, which could be decreased, and the realizability and the controllable of The Novel Numerical Control fiber vector-sum microwave photonic phase shifter could be also enhanced. The affections on the phase and amplitude of the signals which from the change of division index and frequency were analyzed. The phase shift above 140 was achieved. The numerical control voltage source was designed to adjust the driving voltage of the directional coupler to change the light intensity in the fiber. The numerical control on the phase of the output signal was achieved finally. This microwave photonic phase shifter can be realized easily and has some novelty.