Hydraulic losses of mixed-flow pump impellers with four different specific speed impellers were measured near the respective best efficiency point .The measured radial variations of the hydraulic loss at the impeller exit were compared with those calculated y the two-dimensional boundary layer calculation procedure under the support of the quasi three-dimensional potential flow analysis. The calculated hydraulic losses at the impeller downstream section showed good agreement with the measured ones in the case of good agreement between the calculated and measured velocity distributions at the impeller inlet. In addition, the measured data were rearranged to get the information on the reasonable choice for the casing and hub cone angle as well as blade loading.