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A development of a large launch vehicle (H-II) started in 1985. The first stage of this launch vehicle uses a liquid oxygen (LOX)/hydrogen (LH2) engine (LE-7), which generates 1,180 KN in thrust. The National Aerospace Laboratory (NAL) takes charge of the LOX turbopump development till the prototype engine is completed. The LOX turbopump consists of a main pump, a preburner pump, and a single stage impulse turbine. The design rotational speed is 20,000 rpm, and the delivery pressure of the main pump is 20.3 MPa and the preburner pressure is 11.4 MPa, and the flow rate is 229.1 kg/s. The high rotational speed, large flow rate, and low suction pressure of the main pump require the combination of a cavitating inducer with three swept back helical blades and a main impeller. In order to design a high pressure and a high efficiency pump, it is necessary to analyze the pump blade passage flows in detail, using a three dimensional flow analysis method. The design method and the experiment, which was carried out using liquid nitrogen and liquid oxygen at the turbopump test facility of the NAL Kakuda Branch are described. The design method combines a streamline analysis and a blade to blade analysis. The predicted pump head coefficients are in reasonable agreement with the experimental results considering the pump efficiency. Because a large amount of data are usually necessary to calculate three dimensional flows, a method of calculating blade shapes correctly only by giving two blade angles at the impeller inlet and outlet is developed.