We propose a novel approach to fabricate an array of three-dimensional waveguides in lithium niobate by employ ing illuminations of a pair of mutually coherent or incoherent two-beam interference pattes. Adjusting periods of the pattes and the angle between the grating vectors of the two pattes, we find that arrays of square, rectangular or parallelogrammic waveguides can be created. An array of rectangular waveguides is demonstrated in an iron doped lithium niobate by the double exposures of two-beam interference pattes with different orienta tions.