Heat preservation principle: multi-layer heat insulation material is used in the interlayer to reduce radiation heat transfer; (liquid nitrogen vacuum tube) the interlayer is pumped into high vacuum state to reduce convection heat transfer; The inner and outer tubes are separated by supporting materials with low thermal conductivity to reduce solid heat transfer and achieve high vacuum multi-layer insulation effect. Through the high vacuum multi-layer adiabatic form of the inner tube to control the loss of cold to a low limit, greatly reduce the inner tube transmission medium loss to meet the delivery of low-temperature liquid. Therefore, the vacuum tube is a kind of low-temperature liquid transportation pipeline for liquid oxygen, liquid nitrogen, liquid argon, LNG and so on. Liquid nitrogen vacuum thermostat tube features: very low loss rate of liquid nitrogen; inside and outside the tube are used stainless steel materials, good strength; male and female joint connection, heat leakage is small; light sandwich materials and adsorbent with use, the sandwich has a long vacuum life.