Insufficient understanding of the correlation between pump and pump as turbine (PAT) performance is a major problem encountered in the PAT selection and design. Therefore, establishment of accurate PAT performance prediction methods is necessary. In this paper, theoretical analysis of the relationship between pump and PAT performance was first performed. A theoretical method of predicting PAT performance is developed using theoretical analysis and empirical correlation. In the next step, computational fluid dynamics (CFD) was adopted in the direct and reverse modes performance prediction of a single stage centrifugal pump. To give a more accurate CFD result, all domains within the PAT control volume were modeled and hexahedral structured mesh was generated during CFD simulation. Complete performance curves of its pump and turbine modes were acquired. To verify the accuracy of theoretical and numerical prediction methods, the pump was manufactured and tested on a PAT open test rig. Results comparison and discussion of the theoretical, numerical and some other methods with experimental data were carried out. Eventually, relatively accurate theoretical and numerical PAT performance prediction methods were developed. (C) 2012 Elsevier Ltd. All rights reserved.