The volume expansion of the stuff (e. g. tobacco stem) is of great importance to an increase in the product quality and a decrease in the production cost This paper puts forward the basic configuration and the expansion mechanism of a new type of jet pressurization evaporation expansion apparatus. By the thermodynamic calculation of the apparatus, we give variations in steam pressure on various cross sections of the flow system for the apparatus, manufacture a sample machine, and finish run tests of the machine. The test results show that the apparatus may make the relative increase in fill value of tobacco stem higher than 75%. and may cause the steam consumption required in the expansion process of each kilogram stem to reduced about 40% compared with conventional expansion apparatus. Additionally, the configuration of the apparatus is simple and small, its cost of manufacture is very low, and both its operation and maintenance are extremely convenient. The volume expansion of the stuff (eg tobacco stem) is of great importance to an increase in the product quality and a decrease in the production cost This paper puts forward the basic configuration and the expansion mechanism of a new type of jet pressurization evaporation expansion apparatus . By the thermodynamic calculation of the apparatus, we give variations in steam pressure on various cross sections of the flow system for the apparatus, manufacture a sample machine, and finish run tests of the machine. The test results show that the apparatus may make the relative increase in fill value of tobacco stem higher than 75%. and may cause the steam consumption required in the expansion process of each kilogram stem to reduced about 40% compared with conventional expansion apparatus. , its cost of manufacture is very low, and both its operation and maintenance are extremely convenient.