A phase correction method is presented to remove the phase slope of the sub-holograms caused by the multi-direction illumination on object in digital holography. To improve the resolution of the reconstructed holographic images, two sub-holograms are recorded by using angular multiplexing and their phase slope parameter is obtained by theoretical analysis. Introducing a phase correction parameter to this phase slope, the ideal complex reconstructed image can be obtained by superposing the reconstructed object wave fields of the two sub-holograms. Experimental results demonstrate that the resolution of the reconstructed image can be effectively enhanced.