There are generally two types of biological sample freezing tanks, YDS series liquid nitrogen tanks and YDD series liquid nitrogen tanks. The storage methods and capacities of the two are different; some large laboratories or stem cell sample banks require YDD series stem cell liquid nitrogen tanks to meet their needs. Stem cell liquid nitrogen tanks provide users with a large-capacity, new intelligent, safe and reliable deep-temperature liquid nitrogen storage system. Supports liquid phase and vapor phase compatible storage methods, mainly using vapor phase to preserve biological samples. There is a rotating tray inside the storage liquid nitrogen tank. There is a certain interlayer between the rotating tray and the inner tank. The mezzanine space can hold liquid nitrogen or keep the temperature of the storage space and the mezzanine space isothermal through cold nitrogen vapor, which not only ensures the loss of liquid nitrogen but also avoids sample cross-contamination.