Spot arrays beyond the diffraction limit are required in many optical applications, and the shaping of a light beam into subdiffraction spot arrays can be implemented by diffractive optical elements (DOEs). However, the low light efficiency of spot arrays is undesired in many applications. In this paper, a modified Gerchberg-Saxton algorithm is presented for generating DOEs to realize subdiffraction spot arrays with higher light efficiency. In the simulation, the spot size is reduced to approximately 70%-90% of the diffraction-limited spot, and the corresponding light efficiency is within the range of 20% to 50%. The experimental results are also shown to demonstrate the effectiveness of the proposed algorithm.