The micro miniature refrigerator (MMR) is a novel Joule-Thomson cryocooler manufactured using micromachining technology, and its axial length is significantly shorter than that of traditional JouleThomson cryocoolers used in infrared detectors. MMRs can significantly reduce the size of infrared detectors when they are successfully integrated. To study the working mechanism of MMRs, a microchannel flow calculation model is established considering the high working pressure and significant change in the gas properties along the microchannels, and the calculation model is verified experimentally. The heat transfer characteristics, microchannel distribution, and overall dimensions of the MMRs are further investigated. Furthermore, an MMR prototype is fabricated based on the calculation results and its cooling performance is studied experimentally. The experimental results correspond well to the predictions of the calculation model. The MMR prototype achieved cooling temperatures of 110 K and 119 K under 10 MPa N2 and Ar working conditions, the cooling power reaches 231 mW and 479 mW, and the cool-down times are 250 s and 70 s, respectively. Consequently, the cooling performance of the MMR prototype is superior to that of the foreign MMR and meets the cooling requirements of infrared detectors.