Abstract: The miniature nitrogen liquefier can meet the requirements of small amount of liquid nitrogen supply in remote areas,field environment,and scientific research laboratories.A nitrogen liquefaction cycle based on low-temperature mixture refrigerator cycle was built and optimized using the genetic algorithm combined with MATLAB and ASPEN HYSYS.And an experiment device was developed and test.The experimental results show that specific power consumption of the nitrogen liquefier is 1.02 kW·h/Land considering the PSA nitrogen generator,that of the entire device is 1.77 kW·h/L.The series of miniature nitrogen liquefiers can achieve the capacity of 5~10 L/h,and can also be customized according to specific needs.Compared with the commercial nitrogen liquefiers,the liquefiers have obvious advantages of low specific power consumption,low cost and high reliability.