Multistage low-temperature refrigerator

The invention relates to the field of low-temperature refrigeration, and discloses a multistage low-temperature refrigerator. The multistage low-temperature refrigerator comprises a discharger assembly, a compressor assembly and a refrigerator housing, wherein the discharger assembly comprises a discharger cylinder and a pair of discharger pistons, the paired discharger pistons are oppositely arranged in the discharger cylinder, the discharger pistons are connected with the discharger cylinder through clearance seal, and the discharger pistons are of a stepped structure respectively; and the compressor assembly comprises a pair of compressor pistons which are oppositely arranged in the refrigerator housing and a compressor cylinder, the compressor pistons are connected with the compressor cylinder through clearance seal, and the port of the compressor cylinder is hermetically and fixedly connected with the refrigerator housing. The multistage low-temperature refrigerator disclosed by the invention is simple in structure, slight in vibration, high in reliability, and capable of reducing losses in a heat regenerator and improving the refrigeration performance.