We present a method to expand the record field of view in the recording process of digital holographic microscopy systems without loss of resolution. A series of incoherent sub-holograms covering different regions of sample can be recorded in a single frame of the CCD synchronously based on wavelength and polarization multiplexing. The reconstructed images can be obtained with information about different parts of the sample. Thus, the synthetic reconstructed image with a wider field can be achieved by image stitching and fusion technology without any form of scanning. Based on single-exposure working principle, this approach can be used for real-time recording of the dynamic samples without moving CCD, point source and tested samples. Experimental results show that the final synthetic image produced by the system in this paper can be achieved to be close to four times as large as the original record field of view with original resolution.