When utilizing the phase-only spatial light modulator (SLM) for holographic display, the visual impression of reconstructed image is disturbed by multi-order diffraction beams and multi-order reconstructed images because of the pixelated structure of the SLM. After the effects of a pixelated SLM with a limited fill factor on the reconstructed image are analyzed, the method that improves the visual impression of reconstructed image and adjusts the position and size of the image is investigated. Firstly, synthesizing phase-only hologram and digital blazed grating, subsequently adding the phase of the convergent spherical wave, the two focus planes of reconstructed image and the multi-order beams caused by the pixelated structure of the SLM can be separated. Then both the aperture and the high pass filter are used to eliminate the influences of higher diffraction orders, multi-order images and zero order light on the visual impression of reconstructed image simultaneously. Eventually an imaging lens is used to adjust position and size of the reconstructed image. A holographic display system based on liquid crystal on silicon (LCOS) is set up to demonstrate this method. The experimental results show that the final reconstructed image not only has good quality but also has the conveniently adjustable position and size. This method can also be applied to various optical systems based on pixelated SLMs.