Structured illumination formed by modulating the phase and the amplitude of input beams is used to improve the resolution of digital holographic microscopy. According to the properties of structured illumination, bright-field and dark-field recording systems are built. In the bright-field system, an amplitude type sinusoidal grating and scattering elements are used to modulate the high frequency information which overpasses the diffraction limit into the frequency lower than the cut-off frequency, which can be recorded by an imaging system. By shifting the high frequency information to the correct position and combining the low frequency information, the resolution of the reconstructed image can be improved in the process of digital representation. In the dark-field system, both the amplitude and phase of the input beams are modulated by loading different images on a spatial light modulator to generate Laguerre-Gaussian vortex beam, Airy beam and Airy beam with vortex phase. A darkfield condenser used in the system focuses these beams on the sample respectively. It is found that not only the resolution but also the contrast is enhanced.