The design and fabrication method for diffractive microlens array are studied. Based on the research achievement, 256×256 multi-phase diffractive microlens arrays are manufactured for 3～5 μm wavelength. Point spread function and diffractive efficiency of the designed multi-phase diffractive microlens arrays are measured. The diffractive efficiency of 8-phase and 16-phase quartz diffractive microlens arrays are 80.2% and 87.5% respectively, which suggests that the designed multi-phase diffractive microlens arrays can fulfill practical needs.