In the reconstruction of the computer-generated holography, the size of the reconstructed image is small because the pixel size of the spatial light modulators (SLM) is limited. As we know, each point of the phase-only hologram contains all the phase information of the image in computer-generated hologram. A method to enlarge the size of the reconstructed image is proposed. We divide the phase-only SLM into four areas by using spatial multiplexing method, and load the holograms on the corresponding areas of the SLM, respectively. In the optical reproduction, by changing the phase grating that loads onto the corresponding scene hologram, we can adjust the position of the reconstructed image. Therefore, we can achieve large-size reconstruction of the computer-generated hologram without tiling. The experiment verifies the feasibility of the proposed method. We compare the proposed method with other methods and discuss the results.