Abstract: An experimental study is carried out using hydrocarbon refrigerant R600a/R1150.The cryogenic refrigerator is taken as the research object.The characteristics of R600a/R1150 and R600a/R23/R14 mixed refrigerants in the experiment of two-stage Auto-cascade Refrigeration Cycle System are compared and analyzed.Under different working conditions,several mass ratios of mixed refrigerants are compared.The results indicate that the mixed working medium has the optimal performance under the ratio of 62/38.Under this ratio,the temperature of the system can reach-80℃ at 25℃ ambient temperature and-77℃ at 32℃.In the same working condition,the system performance of R600a/R1150 is better than that of R600a/R23/R14.The temperature in the refrigerator of the former is about 2℃ lower than the latter,and the system charge is 36.4%less than that of the latter.