The calculations of an airlift and a jet pump (ejector) working in a two-phase (water/sand stream) mode is executed on the basis of systems of differential equations of the conservation laws suggested by the AUTHORS. The calculations are performed as one-dimensional and stationary. For the calculation of the jet pump the two-phase flow in a vertical pipe was studied followed by the same calculations for the jet pump. Physical and mathematical models are offered for each of the cases. The numerical data calculations allowing to determine the sizes of the ejector’s flow element, and variation of the key physical parameters of a two-phase stream lengthwise are carried out. When developing the equations for movement measurement for liquid and solid phases, the classical coefficients of resistance and friction based on Reynolds’s numbers were used. The results of the differential equation solutions are illustrated with graphs. The presented physical and mathematical models of calculation of the airlift and the jet pump are a further advance of methods of calculation of jet devices of this class.