Based on the theory of one\|dimensional separate spatial soliton pair formed in an unbiased serial photorefractive(PR) crystal circuit consis-ting of two PR crystals connected by electrodes, the mutual dependences of the two solitons are investigated. When a dark soliton beam and a Gaussian beam are incident on the two PR crystals, respectively, the effects of changing the peak intensity of the dark soliton on the propagating property of the Gaussian beam are discussed by numerical calculations. The result shows that the dynamical evolution of Gaussian beam in one crystal can be modulated by changing the intensity of the dark soliton in the other in the circuit. By this way one can determine whether the Gaussian beam could evolve into a solitary wave or ont.