Abstract: The annular fluid jet device uses the energy in the oil transported to make jet fluid, which enables the deposit at the bottom of a tank to be suspended so that it is carried away alongside with oil, functioning as tank cleaners. The article deals mainly with the structure operating principle, desigh calculation, test results, working conditions and economic efficiency of such a deveice. In comparison with the propeller-like agitator in use at present in China, it is better in such ways as of simple structure, even distrbution of energy and freedom from dead corner.