The evolution of Gaussian beams in photorefractive crystal biased by spatial modulation electric filed is investigated. The results show that the filed distribution of the Gaussian beams is modulated and varies with the applied external field. The interactions of the beams with same-phase, anti-phase and phase difference of π/2 in the photorefractive crystal are studied emphatically. Many novel and practical properties are found when the distribution of applied external field is linearly increased. By adjusting the distribution of external electric field, one can make the separation of the same-phase beams closer without mergence, deflection of the anti-phase beams and power transfer of the beams with phase difference of π/2 controllable. In simulation, it is found that the linearly increased field distribution can be substituted by a stopped one, so it is possible to realize it in engineering.