A new method for estimating two-dimensional direction-of-arrival based on a special linear array is presented. Rotational invariance of the virtual array can be obtained from rotational invariance of the reference array using the method of two-direction expansion, which improves the array’s expansion ability and eliminate redundant data of the forth-order cumulant matrix. Using the new method, the signal subspace can be estimated from only two forth-order cumulant matrices. DOA estimation can be achieved by the 2D ESPRIT method. The theoretical analysis and simulation results show that this method has low computation cost, excellent expansion ability, high estimation precision, and good practicality.