The characteristics and the structure of the spatial flow in an axial turbine stage with a negative gradient of the degree of reactivity were explored. A calculation model of the stage was constructed and 3-D testing gas-dynamic calculations in ANSYS CFX were performed. The structure of the flow between blade rows and in the blade–to–blade sections on different sections along the radius were analyzed under nominal conditions. The graphs of the efficiency index and the degree of reactivity depending on the frequency of the rotor are presented. The distribution of flow parameters (α1, β1 and α2 angles; the degree of reactivity, coefficients of flow velocity for the guide vanes and the impellers) are given by the height of the blade. The calculation results are compared with the experimental data. We have concluded that it seems feasible to use ANSYS CFX to determine the characteristics and spatial patterns of flow in the turbine stage with the negative gradient of the degree of reactivity. The merits of this type of stage compared to the stage of conventional type are formulated.