A theoretical model of the scanning control for a fiber-optic interferometric phased array based on phase modulation is proposed to overcome the limitation of scanning control for a fiber-optic interferometric phased array in practice. This model uses optical fibers as the phased-array elements, adopts paraxial and far-field approximations, and uses the scanning-control voltage loaded on the phase modulator to realize the scanning of the beam. A [-π, π] charging scheme of scanning voltage is proposed. The relationship among scanning angle, element spacing, and parameters of the phase modulator is numerically analyzed, and the influences of the phased-array path number and modulation coefficient on scanning resolution are verified numerically as well. Results show that the voltage is controlled within ±Vπ (half-wave voltage) by the [-π, π] charging scheme; when the spacing of the phased-array elements is constant, the scanning angle increases linearly with an increase in the length-to-height ratio of the phase modulator in the small-angle range; the higher the number of phased-array beams and the smaller the modulation coefficient, the higher the resolution. The maximum scanning angle can reach 0.1 rad when the length-to-height ratio of the phase modulator is 10 3 orders of magnitude and the spacing of the fiber-array elements is 125 μm, and the scanning resolution is 210 when the modulation coefficient is 0.3 and the number of fiber-optic elements is 50.