It is important to know in which section the stall of impeller and guide vane occurs at first. It seems that the stall is closely connected with the distribution of lift on the blade. Though at the root solidity is small, large lift coefficient is frequently required, we also introduce the expression for stall condition at the root and prepare certain diagrams convenient for application to design. By using the diagrams we can easily know whether the flow and pressure coefficient at the design point are safe or not for stall. And we introduce a method of assuming the pressure-and efficiency-discharge characteristic curve, especially at once predicting stall point and show examples.