Heat preservation principle: multilayer thermal insulation material is used in the interlayer to reduce radiation heat transfer; (liquid nitrogen vacuum tube) interlayer is pumped into a high vacuum state to reduce convective heat transfer; The inner and outer tubes are separated by support materials with low thermal conductivity to reduce solid heat transfer, thus achieving the effect of high vacuum multilayer insulation. Through the form of high vacuum multilayer insulation, the inner tube cooling loss is controlled to a low limit, and the loss of the inner tube conveying medium is reduced to a large extent, so as to meet the delivery of low-temperature liquid. Therefore, vacuum tube is a kind of conveying pipe for low temperature liquid such as liquid oxygen, liquid nitrogen, liquid argon and LNG.