Abstract: This paper describes the development of a big refrigeration capacity two stage G—M refrigerator which uses magnetic material Er₃ Ni as 2nd regenerator matrix.T his refrigerator can supply the cooling capacity for the cooling background of the space environmental simulating equipment.It requirements of the space environmental thermal simulating tests of the radiant cooler.By optimizing the machine structure and the operating parameters，the no-load temperature of the second stage is 5.5K when the cycle frequency is 40r／min.T he net cooling capacity of 15.4W has been achieved at 20K.It proves that the improvement of the refrigeration performance with magnetic regenerator materials is efficient.