Cold-carrying circulation system and freezing and thawing machine

The utility model belongs to the technical field of refrigeration equipment, and particularly relates to a cold carrying circulation system and a freezing and thawing machine. The utility model aims to solve the problem that ice crystals are easy to generate in a cold-carrying circulating system. The cold-carrying circulation system comprises a cold-carrying circulation pipeline, a buffer tank and a surge tank. The buffer tank is connected with the cold-carrying circulation pipeline and used for storing the secondary refrigerant overflowing from the cold-carrying circulation pipeline. The surge tank is communicated with the buffer tank, and the surge tank is switched between a first form and a second form. When the surge tank is in the first form, the volume of the surge tank is the first volume. And under the condition that the surge tank is in the second form, the volume of the surge tank is a second volume, and the second volume is larger than the first volume. According to the secondary cooling circulatio