Abstract: Based on Eulue's equation and Wu's theory a method for calculating quasi 3-D flow system through multi-component parts in pumps and water turbines is discussed. The equation is solved by means of FEM. The influences of a runner. And its parts ahead and behind on flow field have been taken into consideration in calculation. The flow field ahead of a runner' of course, is necessary for solution of flow field in the runner, that can be worked out without using experimantal data. By this way, a more accurate result of flow field in the runner may be obtained. This seems to be valuable for machines, which have parts formed of blades in front of the runner, A comparison between the calculation result and measurement for three kinds of machine has been given in this paper.