In this paper, the performance of a small centrifugal compressor of an UAV at design and off-design operational conditions is estimated by way of advanced commercial CFD code, ANSYS-CFX-16. Then, the gained performance is compared with published predicted performance using approximate method[1, 2]. The engine used is JetCat P200-sx, which is a single spool turbojet. Considered off-design regimes include centrifugal compressor operations at 73%, 80%, 85%, 90%, 100% and 103% of the design point rotational speed. Commercial CFD code CFX-16, is used for compressor performance prediction at design and off- design operating conditions. The computational grid is created using Turbo-Grid for compressor parts impeller and vanned diffuser. While for both intake device and vaneless diffuser an unstructured tetrahedral mesh with prism layers along the wall surfaces using ANSYS-ICEM CFD mesh is used to resolve the near-wall boundary layer. To gain a reduction in the computational analysis cost, only one passage is considered as a portion of the computational domain and the model is simulated as a steady state problem. Finally, to detect the surge point at each rotational speed the unsteady simulation on performance predictions of centrifugal compressor is investigated. It is a common practice to use compressor characteristics available in graphical form. These plots can be transformed into empirical equations that can be used in automatic calculation. Such approach was done to predict the same compressor performance[13]. The CFD detailed compressor performance is compared with the mentioned published one. The numerical CFD results illustrate good agreement with the analytical model.